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LaRue Tactical Stealth Sniper System LT-011

12/27/07 - The LaRue Tactical Stealth Sniper System LT-011 is a complete drop-in upper that's ready to swap out with your old one and begin precision shooting. After adding a scope with LaRue mount, of course. The Stealth is LaRue's answer to the demands of the precision AR-Shooter, and was designed with ¾" 100-yard shot groups in mind. The Stealth has exceeded their expectations, and has earned a great reputation for its sub-MOA accuracy, with reports of consistent hits on 4" plates out to 400 yards with 77 grain Mk262 ammunition. Complete Stealth Uppers come expertly-assembled and tested with Receiver, Free-float Handguard, Barrel, Low-Profile Gas block and Tube, Mil-Contract M16 Bolt Carrier Group and Charging Handle.

Stealth Receiver - The heart of an accurate rifle is the barrel, but it still needs a strong backbone. The Stealth Sniper System is assembled with the Stealth Billet Upper receiver (LT-007), which I featured on the previous page. Summarizing what I wrote before (if you want to see additional photos, go here), the Stealth Billet upper is a beautiful piece of machine work. The Stealth upper was designed to retain the overall 'look' of a standard receiver; and reveal its origin only upon close inspection to a trained eye. LaRue's intention was to produce a very high quality upper receiver for precision builds. That meant a 'square/true' receiver, with all critical datums and features/surfaces square to each other, with no misalignment of the bore. While it can be debated whether and how having a 'trued-up' receiver has a noticeable effect on accuracy, it sure is nice to know you're starting out with one. It definitely doesn't hurt. Reduced receiver flex is another step towards increased accuracy/consistency under different shooting conditions and positions, and the Stealth receiver has been beefed up and reinforced in those areas which LaRue feel are the important ones.

Every surface on the Stealth receiver is machined, and you can see the subtle evidence of the tool paths, which I think give it a nice aesthetic. The Stealth Receiver is machined out of 7075 T6 and has a mil-spec type III hard anodized finish, which feels very slick over the machined surface. There are no sharp edges on this piece either. The Stealth Sniper System uses a receiver in the A3 configuration, which means no M4 feed ramp cuts. The Stealth weighs one ounce more than a standard M4 receiver, from the beefing up of critical areas. T-numbers are laser engraved on the top, along with the small Stealth™ lettering in the last slot, usually covered by the BUIS. 'LARUE' is subtly machined into the right side of the receiver just in front of the charging handle.

Some additional differences when comparing the Stealth to a standard receiver are:

  • Geometry of the shell deflector - it's been beefed up and is slightly larger than the standard deflector. The transition from deflector to body is also smoothed out.
  • Ejection port cover rod retention - beefed up a LOT and the c-clip retainer has been relocated to just in front of the cover, rather than in front of the lug. It has a cleaner overall look.
  • Areas around ejection port and cam pin bump have been beefed up.
  • A small scallop on the left side has been added to provide clearance for the bolt release catch which indicates that the wall thickness of the receiver has been increased in that area. The wall thickness of the entire receiver 'tube' in which the bolt carrier rides has been increased, by comparing the diameter of the Stealth to a standard.
  • Transitions between surfaces more 'radiused' and smoothed out.

The LaRue Stealth Sniper System upper

16" barrel and 13.2" hand guard

Bottom view

Barrel extension close up

Standard feed ramps


Barrel - The heart of the system is the barrel, and LaRue Stealth Barrels are Wylde-chambered in 5.56mm, 1-in-8 twist polygonal rifling in medium-weight contour using LW-50 (Lothar Walther) Stainless. From LaRue's web site: In the late 1980's, it was realized that there were erosion and short barrel-life problems with 416 Stainless in the calibers operating at 65K psi. 410 Stainless also had issues. LW-50 became the answer. LW-50 lacks sulphur, which in high quantity, created short throat-life in other Stainless Steels. LW-50 can also be heat-treated to a point that makes it near-optimal in all forms of rifle barrels. LW-50 has been proven for over 15 years, in military and civilian uses ranging from sniper, tactical, target, and other high-performance applications where long life and accuracy are critical.

The Stealth Sniper System Uppers is available in 12", 16", 18" & 20" barrel lengths with the LT hand guard length of your choice. LaRue's Low Profile gas block is used on all Stealth Sniper Systems. The barrels are bead-blasted with a non-glare finish, and are marked '8P' (1 in 8 twist, Polygonal) outlined by the state of Texas. As you might be able to make out in the photo below on the right, polygonal rifling differs from standard rifling (lands and grooves) by having no sharp edges. The transition between the lands and grooves are smoothed out. Instead of the sharp cornered land, it's more of a curve. Some of the claimed advantages of polygonal rifling are less copper fouling, better gas sealing between the bullet and the bore, and thus, higher velocities. It's shown here with a 16" barrel. It's furnished with a standard USGI A2 flash hider.

LaRue low profile gas block

Mil-spec carrier and bolt

QD sling swivel socket on hand guard

8P barrel marking

Polygonal rifling

Hand guard - Of course, the Stealth Sniper System uses none other than LaRue's own Free-Float Integrated Rail System, reviewed in detail previously here. It's CNC-machined out of aluminum, and available for the Stealth System in 7.0", 9.0", 10.0", 11.0", 12.0", and 13.2" lengths. They use a two-pin proprietary barrel nut system with a locking anti-slip plate, which prevents the barrel nut from loosening. Once the rail is properly installed, there is no chance of movement whatsoever. Everything locks into place rock-solid. This is vital when utilizing lasers, optics and other hardware. The side and bottom rails are tucked closer to the barrel, keeping the profile narrower and more streamlined. I measured the rails to be 2.0" across and 2.2" in height (same as the LMT MRP) - less than all the other rail systems including the KAC RIS and Troy. I do like the feel of a slimmer hand guard as I've got small hands and a narrower rail is easier for me to get my hands around, especially with rail panels. There's always that compromise between radiated heat from a hot barrel and comfort (the closer to the barrel the hotter it can get), but the LaRue hand guards are extensively ventilated to allow airflow. The rails have laser engraved "T-numbered" positions, and also the KAC panel 'cuts' at each end which enable the KAC panel clip to snap in place. LaRue hand guards also include a QD sling-swivel socket integrally-mounted at the base of each side for convenient mounting 2-point slings.

The Stealth Sniper System can be had in different barrel and hand guard combinations. The recommended barrel length / hand guard combinations are:
20" Barrel: 13.2" & 12.0" Hand guards
18" Barrel: 13.2", 12.0", 11.0" & 10.0" Hand guards
16" Barrel: 13.2", 12.0", 11.0" & 10.0" Hand guards
12" Barrel: 11.0", 11.0" Gooseneck, 10.0", 9.0" & 7.0" Hand guards

An excellent illustration showing the different combinations is on LaRue's web sitehere. In this write up, the Stealth Sniper System shown has a 16" barrel combined with a 13.2" hand guard

M16 Bolt-Carrier Group - The bolt carrier group used in the Stealth Sniper System is the same mil-spec hardware used military-wide. Additionally, LT assembly enhancements greatly minimize bolt-related failures. Mil-spec gas-key contact areas are surface-ground flat for zero gas leakage and then max-staked to eliminate all chances of vibration-induced failures.

Assembly and Testing - Every LT Stealth Sniper System is precision-assembled and as part of LaRue's QA procedure, goes through a final 10-round live-fire function test before being tube-packaged.

Stealth Sniper System with harris bipod

Leupold Mark 4 M1-10X

with Bobro bipod and DNTC brake

Installing the Stealth Sniper System upper took less than 10 seconds. I grabbed my Leupold Mark 4 M1-10X scope in LaRue SPR-S mount and put it on the Stealth. I really like the compact length of the 16" barrel combined with the protection of the 13.2" hand guard as it makes for a very handy overall length. The low profile gas block is completely covered and the extra length of the hand guard gives me a lot of options for positioning the bipod or any accessories I might choose to add later. I added a Harris bipod and it was time to take it to the range. The Stealth Sniper System upper is just a solid feeling, good looking package and oozes of the typical LaRue quality.

I was revved up and excited to break it in and shoot some groups, but unfortunately when I got to the range, the winds kicked up just as I broke the Stealth out. I also spent a good portion of the time at the range breaking in the barrel, and with 20-30 mph gusts of wind, I had little hope of getting tight groups. I could see my target stand blowing back and forth from the wind through the scope and it was rather frustrating. Even so, I tried to shoot some groups in between gusts, and was able to get a three 5-shot groups ranging from 1" to 1.2", strung out horizontally, which was to be expected. I was shooting both Winchester 55gr and Black Hills 68gr Match and didn't notice any difference under those conditions. Vertical spread was around 0.7" for the groups which was encouraging. I used the rest of the time at the range to plink at steel targets from 200-400 yards, which I hit easily as they were large (12"-18"), and the Stealth functioned perfectly without a hitch with both types of ammo. Back home, I found that the bore didn't have much fouling and it seemed easier to clean than normal rifling. I'm very eager to give it another go at the next range trip, and hope that I'll be blessed with a calm day.

1/6/08 - Well, we were blessed with a calm day, but it was a bit damp. Nevertheless, in the middle of a lunch break during a group shoot, I broke out the Stealth upper to give it another go. I brought the same Black Hills 68gr match, and some UMC 55gr 'blasting' ammo. Target distance was 100 yds, shooting from a bipod and rear bean bag support. Surprisingly, the UMC ammo definitely got the tighter groups than the Black Hills. I didn't want to admit it to myself before (as BH ammo isn't cheap), but I've tried the Black Hills in two other precision uppers and that ammunition has not grouped for me as well as I had anticipated or hoped. Each time, standard 55 gr has done better in the same rifles. All of them were 1 in 8 twist rates. Go figure. I'll have to try a different bullet weight and see what happens.
Anyway, the results are on the target below and I'm pretty happy with them, considering it's standard, non-match ammunition. Two 3-shot groups at .52" and .65" and a 4-shot group at .73", and one 5-shot group at exactly an inch. The upper left 3-shot group was 1.22" but firing quickly. The LaRue Stealth upper claimed it was designed for 3/4" groups and it's proven that capability, strangely enough with 'cheap' ammo.

As an aside, I also took the opportunity to sight in the Optima mini-red dot sight mounted in the LaRue J-Point/Dr Optics Scope attachment on the side of the Leupold. I sighted it in at 50 yds and did some 'run and gun' drills with it from about 40 yds to 10 yds, and it was more accurate than I had expected. I had some some shooting with it before, but all static (no running to different distances and shooting from different positions). The Stealth Upper with its 16" barrel was handy enough maneuverable shorter distances, and the Optima was accurate enough not to be just an 'emergency' sight, but viable for anything under 50 yds for quick shots. That scope is staying on the Stealth upper and makes a great package.

100 yds target, 55gr UMC


Daniel Defense AR15 Omega Rail 7.0 (Carbine)

1/18/08 - Daniel Defense, Inc., the Savannah, Georgia manufacturer of parts and accessories for the AR15 and AR10 weapons systems has introduced their Omega Rail 7.0 (Carbine) for the AR-15. Looking a lot like their free floating Lite Rail reviewed on the previous page, the Omega differs from the other DD rails by the fact that it does not require removal of the front sight base/gas block or replacement of the barrel nut, and can be installed on any standard AR-15 with delta ring. One of the obstacles that some users face when choosing a rail system is that they do not want, or are not permitted to modify their rifle. Most free float rail systems require some modification or gunsmithing to install. The Omega rail allows the user to install a free floating rail system that requires no modification to the host weapon and is so easy that if you can take your plastic hand guards off, there's a very good chance you can install the Omega.

The Omega Rail is machined from 6061-T6 aluminum and finished with a black Mil-Spec type III hard anodize. Indexing marks/'T-numbers' are laser engraved on all the Mil-Spec 1913 rails. The Omega rail isn't just a 'converted' version of one of DD's rail extrusions - the width across the rails is even slimmer than the Lite rail at approx 1.9". This is possibly the slimmest rail I've ever encountered (across). The height is 2.4" from top rail to bottom rail. The hand guard is symmetrical in cross section, with the top and bottom rails the same height/distance from the boreline. The top rail of the Omega extends back over the delta ring to meet the upper receiver rail for an uninterrupted/'monolithic' look. It's a featherweight 7.5 oz.

Parts - The Omega rail comes complete, ready to install on any standard carbine upper. The only other tool needed, other than the provided allen wrench is a flathead screwdriver. The hand guard has two parts - and upper rail and a lower rail. The upper rail has an integral QD sling swivel mount at the rear, which limits rotation of the swivel. The top rail is 7" long. The lower rail nest into the upper rail, and is removable. There are four helicoils in the lower rail in which four flat head screws are used to secure the lower rail to the upper rail. Both upper and lower halves have a groove in the back in which the barrel nut toothed flange sits. There are also two setscrews at the rear of both rails which tighten against the front of the barrel nut.


Omega Rail components

Rear quarter view

Front quarter/top view

Upper and lower halves

Rear of rails

The first step to installing the Omega rail is to remove the stock plastic hand guards, of course, by pulling back on the delta ring. The Omega upper rail is then installed, by pulling back on the delta ring again, and placing the groove at the rear of the upper rail over the barrel nut teeth, pressing down then releasing the delta ring. The lower rail is installed the same way. Fit between the upper and lower rails is perfect - they slide together with just the correct tension. Not too tight, and absolutely no rattle. The four flathead screws are then used to secure the lower rail to the upper.
Using the provided allen wrench, the two set screws on the upper are tightened slightly which causes the rail to tilt down as they bear against the front of the barrel nut. Then the ones on the lower rail are brought to touch off. The set screws are progressively tightened so that the rail is level and in alignment with the upper receiver rail, and all four set screws are tight. If you need to remove the lower rail at some other time, the screws should be backed off first.

Upper rail installed

Lower rail installed

Assembled rifle

Once installed, the Omega is rock solid, and will not move. Accessories can be mounted on it like any other rail. The Omega also comes with three santoprene 'ladder' rail covers to protect the rails. They can be shortened by cutting to length. The Omega is another good-looking, well designed and made product from Daniel Defense which should be very popular with AR-15 owners that want the convenience of a 100% drop-in free floating rail with no modification to the host weapon.


Primary Weapon Systems AR15 Piston Conversion

5/4/08 - Primary Weapons Systems (PWS), the same guys that produce the excellent DNTC and FSC556 muzzle brakes for the AR15, have introduced their piston system for the AR15. Having dealt with the AK system for some time, they wanted to bring the reliability of the AK to the AR15 platform with its superior ergonomics. Now, some would argue that a piston system for an AR15 is unnecessary except for some specific applications, but the market has shown that even if people don't necessarily need one, they want the option of having one. Gene Stoner's direct gas impingement system of the AR15 has proved to be a very reliable one, as long as it's kept properly lubricated and fed with high quality ammo. Even so, the quest to improve upon that system under more conditions has led to the development of piston systems for the platform, like HK with its 416 and various other piston upper manufacturers. Whether or not they're improvements over the original DI system can only be answered by the passage of time during which these new system prove themselves. Some have been complete replacement upper assemblies, others have been retrofit systems requiring minor modifications. The PWS system falls into that category - it's a retrofit system that can be installed on an existing DI upper or on a brand new build. It's not a drop-in system - it must be installed by PWS or an approved installer.

Piston systems are nothing new; numerous landmark firearms employ them, like the AK-47 and all its variants, FN FAL, M1 Garand, M14. New weapons like SCAR or Magpul's Masada continue to utilize gas piston systems, but these have been designed from the ground up, not as retrofits. As far as I'm aware of, no recently designed new weapon (in the past decade or two) has utilized a direct impingement system even though Stoner's patent expired 30 years ago. So, many people believe that a piston system has a lot going for it, and that venting the gas elsewhere instead of inside the upper receiver of the rifle is a good idea. Retrofit piston systems for the AR are not new either (remember the Rhino in the early 80's?), but piston uppers are still 'new', relatively speaking. PWS's classifies their piston system as a short stroke type, as the piston is not connected to the operating rod and only travels a short distance before it hits the stop and the excess gas is vented.

Is an overhead piston system better than the DI system on an AR? Well, I'm going to step back and stay out of that discussion - there are proponents of both systems and both have argued back and forth over which one is more reliable, why one is needed or not etc. 'If it ain't broke, don't fix it' is one of the arguments against developing a piston system for the AR15. If something can be improved on, why not? As an engineer, I see nothing wrong with someone trying out new designs to address real or perceived issues in existing systems, and I'm always eager to see how they work. So, when Todd at PWS told me of their piston system they were developing for the AR back in May '07, I was all ears.

PWS Prototype (or Gen I) Gas Piston System Conversion

After about 3 months, in August of '07, Todd told me that they'd be getting ready to perform the conversion with the first run of kits (which were still sort of prototypes). All conversions are done in-house or by a PWS certified installer. Instead of converting an existing upper, I decided to send Todd all new components (16" mid length barrel, Vltor MUR upper receiver, bolt and carrier, and Daniel Defense's excellent Lite Rail 9.0 hand guard). I received the assembled upper in early January '08. Shown below is my upper next to a friend's. I chose a mid length gas system instead of a carbine one, as I figured it'd be a softer shooting weapon.

The PWS Gen I conversion consisted of a new gas block with an adjustable/removable gas plug. The gas plug had a spring loaded knob on it, which was pushed down to unlock it and rotate it from one position to another, or remove the plug from the block completely. A piston tube was welded to the rear of the gas block, and housed the small piston and 'mothered' the operating rod. The gas block was taper pinned to the barrel, and featured a rail on top. The plug could be adjusted to any of three settings - 'normal', 'suppressor' (reduced gas) and 'off' (no gas).

My PWS-converted upper

Gen I gas block

Adjustable knob/plug

Plug and piston

The bolt carrier was a standard carrier with a brand new operating rod key with op rod attached where the gas key was. A stainless steel shear pin was used to take up some of the shear load in addition to the two screws holding the key to the carrier. The pin is under the key and goes into a hole on the top of the carrier. The operating rod is fully supported by the piston tube.

Carrier with operating rod

Close up of carrier

Complete rifle

Sighting in

Operation - At rest, the piston was in its most forward position, against the back of the gas plug. As the rifle was fired, the gas bled off from the barrel port entered the gas block and hollow plug, pushing the piston and operating rod backwards. The operating rod was attached to the carrier, which started moving back, and went through the extraction and loading cycle. The piston stopped about 3/4" from its forward position where excess gas was vented out a port in the piston tube. The carrier would move forward again with the operating rod, pushing the piston back towards the front where everything would stop.

At the range, I sighted in the rifle and started shooting it. I've fired both LWRC and POF piston uppers, and I felt that they both had a slightly harsher felt recoil impulse than DI carbines. With the PWS conversion, I was pleasantly to find that it was comparable to a DI system in impulse. This could also be due to the mid length gas system. I shot it side by side with my friend's PWS carbine-length system and it had noticeably softer recoil. I was also running an enidine buffer and the PWS FSC556, which both made a difference. Unfortunately, after about 5 full mags, the piston tube started to shift backwards, causing the rifle to short stroke. This was due to the weld which secured the piston tube inside the gas block coming loose. Afterwards, I spoke to Todd about it, and he was aware of some prototype tubes that had weak welds, and they already had the fix for it. I sent the upper back, and they fixed it, test fired it, then shipped it back to me within the week. I did not have a chance to test fire it before the SHOT Show in February where I met up with Todd. That's when he showed me the changes they had made to the design, based on all the prototype testing and feedback. Quite a few changes were made, which are covered below.

When I got back from the SHOT show, I was able to go to the range and test out the repaired (but obsolete) Gen I system again. This time, it functioned perfectly for all 250 rounds I put through it. Not many rounds, I know, but I was going to send the upper back to be updated to the Gen II (production system) anyways. So, when Todd gave me the go-ahead to send my upper back in early March, back it went.

Production (or Gen II) Gas Piston System Conversion

So, a couple of weeks later, I got my upper back again, with the updated Production/Gen II PWS Piston conversion. Here are some of the differences between the Gen I prototype shown above and the Gen II production version:

  • The gas block is now set screwed instead of taper pinned. Now, this is going to be a sore point with some customers who will not trust anything but taper pins. I'm also of the feeling that with a piston system, taper pins are the way to go. However, the PWS set screws don't simply tighten into the surface of the barrel or shallow dimples; they actually go down about .100", which is as deep as taper pins. Todd acknowledges that there will be questions about this decision and has stated "While many may feel that this will not hold, we can assure that that the 1/4” set screws we are using that sink in as deep as taper pins and hold the gas block on just as well and actually create a tighter seal resulting in better overall function."
  • The gas/piston tube is now one piece (instead of being welded into the gas block) and is removable for easier cleaning of the system. This eliminates the issue I had with the weld on the Gen I prototype.
  • The gas adjustment knob now uses a cam lever instead of pushing down on it. This results in a beefier knob making it easier to get the tube out when the system is hot or dirty. The gas tube, piston, lug pin and adjustment knob become one unit prior to installation. The gas tube assembly is simply inserted into the end of the gas block allowing the lugs to move into the interior channels of the gas block. The gas knob adjustment lever is then moved into the appropriate slot (suppressed or unsuppressed) and the system is ready.
  • The piston has been completely redesigned. The first few Gen II conversions went out with a stainless steel piston. It was found that at higher temperatures on short barrels under prolonged full auto fire, the stainless piston would deform. PWS sent out replacement pistons which were made from the original material; heat treated tool steel (see photo below). If you have a stainless piston, discard it. Do not use it.

Installation - The retro-fit work must be done by PWS or a PWS-certified installer on the customer's upper. It can be done on used or new components. Like the Gen I, the retro-fit system is installed by fitting the modified carrier key and anti-shear pin on the customer's existing bolt carrier. The operating rod is pressure fit into the carrier key. The PWS gas block assembly is installed in place. Note that PWS has found that opening the gas port in the barrel approximately .010" leads to better overall function of the weapon system. This is done by using a set of 3 reamers that are progressively larger to maintain the integrity of chrome lined barrels.

PWS conversion components

Op rod 'mothered' in tube

Same upper with Gen 2 conversion

Gas Knob in 'unsuppressed' position

'Restricted/Suppressed' setting

Description - The photos above and below illustrate the PWS system. The gas adjustment knob has a spring loaded plunger lock on it which engages slots on either the left or right side of the gas block. When rotated with the O symbol on top, the knob is in it's normal setting for unsuppressed fire. By depressing the plunger, the knob is rotated 180° to the left side so the dash ' -' symbol is on top. This restricts the amount of gas entering the gas block.
To remove the tube and knob assembly, the lever is depressed and rotated to the 12 o'clock position. The assembly is then slid out the front. A small cross pin holds the knob onto the gas tube. This slides out either side and the knob is removed from the tube. The piston can then be removed. Reassembly is done in reverse, but you've got to pay attention to the orientation of the cross pin. It has two flats on either end, and these flats must be rotated so that they are vertical. If not, they won't fit into the lugs inside the gas block. The lug pin must also be inserted so that equal amounts protrude from each side. When it's lined up, the whole assembly is inserted into the gas block, and rotated 90° to either side to lock it in.

Knob lever rotated to the top for removal

Knob and tube slide out

Completely disassembled

Operation - According to PWS, when the rifle is fired, the developing gases expand inside of the gas block much like a traditional DI system. The expanding gases push against the short stroke piston which exerts pressure on the operating rod and thus gives momentum to the bolt carrier. Once the piston itself has traveled 3/4", it expels any unused gas from a small vent in the bottom of the piston tube. As the cycle of the action is already in progress, the piston moves to the back of its chamber awaiting the return of the operating rod to push it back into battery.

The following illustrations show how the PWS Piston system works (illustrations courtesy of Primary Weapons Systems)

Piston system diagram

Piston at rest

Piston at mid-stroke

Completing piston stroke

System Features and Notes (from PWS) -

  • Available for Carbine, Mid and Rifle length systems
  • A dual diameter piston for better alignment and less wear
  • Carrier key and anti-shear pin machined from pre-hardened tool steel
  • A mothered operating rod to inhibit flexing or bending
  • QD disassembly for cleaning
  • The operating rod is attached to the carrier to minimize carrier deflection and receiver wear.
  • Adjustable gas system for firing unsuppressed and suppressed
  • All parts are CNC machined and heat treated; no welded or cast parts are used

    As of this writing, the PWS retro-fit system will fit under the following hand guards:
    Modified M4 Hand guards
    Daniel Defense Lite Rail, Omega Rail
    LaRue Tactical Hand guards
    A.R.M.S.® S.I.R.® System
    POF-USA Predator Rail
    The top of the hand guard must not protrude past the gas block. Hand guards that extend past the sides and bottom are acceptable.

* this system is only for the AR15 series rifle in .223/5.56, 7.62x39, or 6.8SPC. PWS will not install it on other calibers.

Initial Range Report - Went to the range with my buddy and put about 250 rounds through it without any issues, shooting off the bench (could only do that at this range). Shot a mix of wolf polymer, prvi partisan and remington through it. One lower had an extra power buffer spring from Sprinco/Tactical Springs and an Enidine buffer, the other had a stock buffer spring and H buffer. The carrier locked back on the last round with both lowers. As before, I could really feel no difference in recoil impulse between the PWS piston upper and a DI upper. My buddy also remarked that the recoil impulse was more like a DI gun than a piston; not as harsh. The bolt and carrier also stayed cooler than that of a DI gun. I did have some observations afterwards:

  • After the shooting session, when it got dirty, I noticed that the gas adjustment knob was difficult to turn by hand due to carbon buildup; just like the gas adjustment on a FN FAL needs a wrench to adjust when dirty. For this reason, PWS designed it to be turned with a 9/16" open end wrench if it gets excessively dirty and difficult to remove.
  • The gas piston would not fall out freely out of the piston tube due to carbon build up - I pushed it out by inserting the operating rod through the back of the gas piston tube, following PWS's recommendation in their user manual. PWS says the piston can be run dry, or lightly lubricated. I'm using machine gunner's lube and it's pretty good.
  • There's slight evidence of carrier tilt at the bottom of the receiver extension tube and also the top bearing surfaces of the bolt carrier; just finish wear for now. This is something to monitor, as well as cam pin wear and receiver wear.
  • Even though they're not needed for the operation of a piston system, and were discarded initially, I decided to leave the gas rings on the bolt, to provide some 'drag' in the bolt carrier during the unlocking and locking processes. I have no proof, but I feel that this can reduce cam pin slam against the carrier. With a DI system, lube on the gas rings can burn off or the area get caked with carbon. This is not an issue with a piston system and all the lube I put there remained throughout the shooting session.

The piston does get dirty with carbon buildup, but it's a lot easier to clean than the back of a bolt. The inside of the receiver, bolt and carrier also remain much cleaner. The inside of the hand guard does get dirty from carbon from venting, but it's no biggie, and can be wiped off if desired. If you're a person that cleans your rifle every time you shoot it, I'd say that the piston upper IS easier and quicker to clean than a DI one. The lube stays on the operating parts and does not burn off. If the PWS system proves to be reliable and durable in the long run, I think it's very promising.

5/25/08 - Follow up Range Report - Put about 400 rounds all on full auto through the PWS upper. I am monitoring the cam pin cut wear on the inside of the upper receiver, and there's wear on the rear edge of the cut but hasn't gotten any worse.

Also shot it alongside the LMT MRP CQB upper with 10.5" barrel and HK 416 with 10" barrel shown here. No hiccups with any of the uppers. The 416 recoil impulse was noticeably harsher than the PWS or MRP. Thanks to Ferfrans.net for the use of their registered receiver.


Addax Tactical GPU (Gas Piston Upper)

11/22/08 - The Addax GPU (Gas Piston Upper) from Addax Tactical is a series of complete uppers utilizing the Primary Weapon Systems (PWS) AR-15 gas piston conversion system combined with high-quality AR-15 parts and components. Addax Tactical is a certified PWS gas system conversion installer, but they wanted to take it a step further. Instead of only assembling components into complete uppers, Addax has been working with PWS to make some refinements to the system which are seen here on their Combat GPU.

Addax Tactical carries a variety of different manufacturer's uppers, but then they looked into offering their own uppers, they chose the PWS gas piston system reviewed previously above to build the uppers with. Addax Tactical can retrofit a customer's existing AR-15 upper with the PWS system, but are concentrating their efforts on building and marketing brand new carbine and mid-length GPUs. The issue with retrofits is the wide variability of components that the customer might supply. There are so many AR-15 parts manufacturers (some that put out mil-spec parts and some who don't) that retrofitting an out-of-spec or low quality upper may not give the best results. Addax Tactical carries a wide selection of high quality AR-15 components and other 'black rifle' accessories from the major manufacturers, so it makes sense to start with all brand new, high quality components and build all their uppers in-house. While Addax can put together just about any configuration desired by the user, they have standardized models in their series of GPU uppers that should fit the needs of most customers. They currently offer two categories; the Standard Series and the Combat Series.

Description - The Standard Series Carbine is the 'basic' model for those who don't need a rail system, and has modified plastic M4 hand guards with heat shields and a 16" barrel. The Combat Series offers the user more choices in barrel and hand guard lengths, utilizing the excellent Daniel Defense Lite rails.

Addax GPU features and specifications:

  • Operating system - PWS Ion-Bonded Gas Piston System
  • Combat Series available in Carbine and Mid-Length versions at the time of this writing with choice of 16", 14.5" and 10.5" barrels. The Standard Carbine has a 16" barrel and carbine-length gas system.
  • Barrels - Sabre Defense, CMMG, White Oak Armament, Lothar-Walther and YHM have been utilized on various GPU models. The current standard barrel for the Combat GPU series is a government profile mil-spec 4150 chrome moly vanadium steel barrel from CMMG.
    Currently chambered in the available calibers: 5.56 NATO (opened up with Ned Christiansen reamer), .223 Wylde (certain models) and 6.8 SPC (5.45x39 and 6.5 Grendel GPU models are currently in development).
  • Upper receivers - The GPU comes standard with a Mil-Spec Forged A3 Flat Top Upper Receiver made from forged 7075-T6 aluminum manufactured to Mil. Specs. It includes extended M4 feed ramps, forward assist, dust cover assembly, and the upper is finished per MIL-A-8625. Non M4 feed ramp upper receivers are used for the Lothar-Walther barrels that have the A2 Barrel Extension. Optional Upper Receivers include the Vltor MUR, with more options currently in work.
  • Bolt carrier group - Addax Tactical utilizes mil-spec Bolt Carrier Groups from White Oak Armament, LMT, CMMG and CMT/STAG in their various models (Full Auto bolt carriers are available as an option). Bolts are MP tested and stamped. Gas rings are left on the bolt.
  • Left Hand Gas Piston Uppers are also available.
  • Muzzle device - Addax Bulldog FSC Compensator comes standard on the Combat Carbine, and Combat Mid-Length GPU's.
  • Every Addax GPU Upper is head-spaced, laser bore sighted, test fired (General Function and General Accuracy) and cleaned before shipping.
  • Addax Tactical 3 Year Limited Warranty on all Components, and a Limited Lifetime Warranty on the Gas Piston System parts from PWS

Addax GPU/PWS Gas Piston System Features:

  • The PWS Gas Piston System utilizes a dual diameter piston for better alignment and less wear
  • The Op-Rod is attached directly to the bolt carrier group to minimize carrier deflection and receiver wear.
  • Hardened tool steel op-rod Carrier key and anti-shear pin
  • A "mothered" operating rod to inhibit flexing or bending (fully surrounded and supported at the front)
  • Easy disassembly for cleaning
  • Two-position/adjustable gas system for firing unsuppressed and suppressed
  • All parts are CNC machined and heat treated; no welded or cast parts are used
  • Addax Tactical 5 Year Limited Warranty on all Components, and a Limited Lifetime Warranty on the Gas Piston System parts from PWS

Combat Mid-Length GPU - I was introduced to Chris, the owner of Addax Tactical, by Todd from Primary Weapons back in July. When we first discussed the possibility of featuring one of the Addax GPU uppers here, I was hesitant as I thought to myself "how is that going to be different from the PWS Gas Piston Conversion write up I just did?" But when we talked further, Chris stated that he wasn't just installing/assembling the same PWS components on uppers, and described the different things that he was working on with PWS for the Addax GPU, like Ion Bonded components and other refinements to the system, I got interested. While my PWS upper has been working well for me so far, I'm always interested in seeing how things might be improved.

Over the next few months, Chris kept me up to date on how the different projects were working out, and I also shared my own input and experiences with my PWS upper that I had also discussed with Todd at PWS. We also picked out the components for the build. I chose to go with a mid length system instead of carbine, the same as my PWS upper. Why not get something different? Because when I shot the carbine and mid-length system side by side, the mid-length one felt softer shooting. Why it feels softer shooting in a non-direct gas impingement system I'm not sure, I can only speculate that it could be due to the greater reciprocating mass with the longer operating rod. Anyways, shown below is the Addax Tactical Combat Mid-length 16" GPU assembly I ended up with. Chris did a very nice job on the build - I think it came out most excellently.

Addax Combat Mid length GPU

Changes to the Addax/PWS Piston System - At first glance, the upper looked very similar to the PWS upper I have. Same barrel length, DD Lite hand guard etc. However, closer examination revealed the differences that Chris had mentioned. Addax had worked over the past 6 months with PWS, providing them with input that helped confirm some things that they were already looking at, working on and incorporating into the current PWS design. PWS took this input, along with other dealers and evaluators, and implemented some changes which will be universal to the PWS components:

  • Finish - All the PWS Gas Piston components are DiamondBlack (PVD coating) coated by IonBond: gas block assembly, gas adjustment knob and cross pin, piston, piston operating rod and carrier key. IonBond was tested on the Addax GPU first, with positive results, and PWS decided to run with it with the blessing of the other PWS dealers/installers. Diamond Black boron carbide is a thin ceramic film applied in a vacuum chamber via physical vapour deposition, and is chip, crack and peel resistant, and impervious to most harsh chemical, and maintains its lubrication longer.
  • Gas block - The new gas block has more meat on it and a smaller bottom opening than the original PWS one to ensure a tighter seal around the barrel. It has the same set screws that are loctited and staked for a semi-permanent installation. Looking at these screws, there's little chance of them coming out. The gas block is not meant to be user-removed - it'll have to go back to the shop if it needs to be. The GPU signature logo is laser engraved on the side of the block for Addax.
  • Gas piston tube - if you compare photos of the original PWS tube to the newer PWS/GPU tube, you can see that they it has a different profile. The thicker diameter at the front of the tube extends further back on and the flutes on the original PWS tube have been deleted. It's easier to remove the tube when dirty now.
  • Op rod carrier key - The new op rod carrier key has been streamlined with all sharp edges now smoothed out, and a slight step down incorporated at the diameter at the front. There is a center channel between the key screws, which have been staked with a chisel. The displaced metal enters the channel and prevents the screws from loosening. The screws are then further staked with a MOAKS tool on the sides. The width of the key where it runs in the charging handle channel has been reduced very slightly to reduce wear. Addax leaves the gas rings on the bolt, even though they're not needed for their original purpose.

GPU piston system components

Ion-bonded parts

Gas adjustment knob

GPU and older PWS carrier keys

Description - The photos above and below illustrate the GPU/PWS system. Operation of the GPU is the same as the PWS. The gas adjustment knob has a spring loaded plunger lock on it which engages slots on either the left or right side of the gas block. When rotated with the O symbol on top, the knob is in it's normal setting for unsuppressed fire. By depressing the plunger, the knob is rotated 180° to the left side so the dash ' -' symbol is on top. This restricts the amount of gas entering the gas block.
To remove the tube and knob assembly, the lever is depressed and rotated to the 12 o'clock position. The assembly is then slid out the front. A small cross pin holds the knob onto the gas tube. This slides out either side and the knob is removed from the tube. The piston can then be removed. Reassembly is done in reverse, but you've got to pay attention to the orientation of the cross pin. It has two flats on either end, and these flats must be rotated so that they are vertical. If not, they won't fit into the lugs inside the gas block. The pin must also be inserted so that equal amounts protrude from each side. When it's lined up, the whole assembly is inserted into the gas block, and rotated 90° to either side to lock it in. The Addax GPU comes with an illustrated manual.

GPU gas block
Set screws at the bottom

Addax Bulldog comp (bottom)

PWS FSC556 (right)

Other Addax GPU components used for this build

Receiver - The Addax GPU comes standard with a forged M4 Flat Top Upper Receiver made from forged 7075-T6 aluminum to Mil. Specs. It has extended M4 feed ramps, forward assist, dust cover assembly, and the upper is finished per MIL-A-8625. However, I really like the Vltor MUR (Modular Upper Receiver), which now comes forged, and happened to have one on hand, so I asked Chris to use it for the build in place of the standard upper receiver.

Barrel and muzzle attachment - I had my choice of available barrels, and decided to go with the same one my first PWS upper was built with, and the current standard choice for the GPU; the CMMG government profile mid-length 16" barrel. I chose it over the Lothar-Walther because it was lighter, and I'd been perfectly happy with it on the previous build. It's more than accurate enough for the type of shooting I'm doing with the carbine; mostly close-range drills. The CMMG barrel is 4150 chrome moly vanadium steel with a chrome lined bore and chamber. Addax reams all their barrels with a Ned Christiansen 5.56 NATO reamer that ensures that the chamber is opened up to a true 5.56 spec (after chroming).
The Combat Series GPU comes standard with the Addax Bulldog FSC Compensator, which PWS makes specially for them. It's essentially a PWS FSC556 which has had the front prongs shortened slightly (hence the name, 'Bulldog'). It has the same compensation of the DNTC/FSC556, with only a slight reduction in flash suppression performance. Besides being a bit shorter, all the sharp edges and corners have been rounded off, giving it a smoother appearance. It bears the Addax logo on the top flat in place of the PWS one.

Hand guard - When I had PWS put together my first upper, I chose the Daniel Defense Lite Rail 9.0, which I was very happy with. Daniel Defense hand guards are light weight and of high quality, and are an excellent choice for a PWS piston upper. The Addax GPU mid length comes standard with the Daniel Defense Lite Rail 12.0 FSPM. This is similar to the Lite Rail 9.0, except that instead of ending just behind the gas block, it extends past it. The opening in the top rail accommodates the front sight post and gas block. This does a couple of things: it protects the gas block at the bottom and sides, and provides some extra rail length. I find the extra rail space useful for mounting my light as far forward as it'll go, plus I just like the way this hand guard looks with a 16" barrel. The hand guard came with three santoprene ladder rail covers.
DD rail hand guards are machined from 6061-T6 aluminum and finished with a black Mil-Spec type III hard anodize. Indexing marks/'T-numbers' are laser engraved on all the Mil-Spec 1913 rails. The quality of machining and finishing is top notch. Width across the rails is approx 2" and height is 2.4". The hand guard is symmetrical in cross section, with the top and bottom rails the same height/distance from the boreline. The Lite 12.0 FSPM is heavily ventilated with lightening holes, to which the light weight can partially be attributed to. A sleeve which provides the six-bolt interface fits into the rear of the rail and is welded in place. The rail free floats off the barrel nut. Since the bolt-up system doesn't utilize a threaded nut to secure the rail to the barrel nut, the top of the rail extends back to the receiver, for an uninterrupted/'monolithic' look.
A small mod has to be done to the hand guard to install the PWS gas block; two small holes are drilled through the rail at the bottom for the set screw access below the gas block. This does not affect the function or integrity of the rail and would probably go unnoticed by most people. The Lite Rail 12.0 FSPM weighs 12.6 oz and utilizes a steel barrel nut. For more details on Daniel Defense Lite Rails, read my write up of the Lite Rail 12.0.

Sights - Like most other uppers, the base price of the GPU does not include sights, but they're available as an option when you 'customize' your GPU. Addax carries a wide variety of sights like LMT, ARMS, Troy, GG&G, MI etc. For the GPU, I picked the new style spring actuated GG&G front and rear flip up sights, as I have most of the other brands. I've had a couple of older GG&G MAD sights for years, but for some reason, they're canted slightly to one side no matter what upper receiver I put them on (requiring a small shim to be installed under the dovetail). The new sights that came with the GPU were straight. Both are spring loaded, and will flip up when the actuator button is pushed on the side. The sights are locked up until the button is pushed and the sights folded down. They lock in the folded position. The sights are very quick to actuate; a push of the button and they pop up. However, this also means that they pop up anytime the button is depressed accidentally. I had the front one pop up a couple of times, but only when handling the upper. At the range, I never had them accidentally pop up when doing transition drills and letting it hang from my sling.
You might also notice that I mounted the front sight on top of the gas block. On the PWS upper I mounted it on the rail. This was because the gas block gets really hot, and a sight mounted there heats up as well. With the Troys, they require you to grab and pull the front sight into position. No problem with gloves, but bare fingered it can be a bit toasty. With the GG&G, which only required a push of the button instead of grabbing the sight, heat wasn't an issue so I mounted it on the gas block.
The front sight has angular cuts on the ears, reminiscent of the facets on the F117-A Stealth fighter. It utilizes the standard A2 square front sight post and elevation adjustments. The rear A2 BUIS has the standard A2-style double peep aperture and military windage knob. Adjustment is dependant on sight radius and is approximately 0.48 MOA on the M16E2 and 0.65 MOA per click on the M4 carbine. Mounted on my mid-length, it's somewhere in-between.

GG&G front and rear spring-loaded BUIS

Rear BUIS up and down

Front BUIS folded

Top view of front end of GPU

Misc - I had put my EoTech back onto my PWS upper so I put the Aimpoint Micro T-1 on the Addax GPU, which I laser bore sighted, along with the flip-up sights. I also replaced the ladder rail covers with TangoDown's SCAR panels, which are my current favourites. I left a ladder rail cover on the top rail. Being a lefty, I installed a Badger Ordnance Tac-Latch onto the charging handle. Also stuck a TangoDown stubby QD vertical grip on it, and a SureFire Scout light.

Initial Range Report - For the initial range trip, I wiped off the excess oil off the piston components (Addax cleans and oils each upper before shipping), as it burns off anyway. I ran the bolt and carrier wet, same as I do with a DI upper. While PWS has run their uppers without lube, I feel that it doesn't hurt, and can only help to provide lubrication for the carrier and bolt. It's still metal to metal contact between moving parts. Any lube I put there stays there, unlike a DI gun, and both the carrier and bolt stay clean. I also grease up the charging handle rod as that helps reduce friction inside the receiver when pulling back on the handle. It's important when using a tac-latch as it's an offset force, not a straight-back one.

As I mentioned above, Addax leaves the gas rings on the bolt, which I did with the PWS upper as well. While they're not needed to provide a seal between the bolt and inside of the carrier, they provide friction between the bolt and carrier, which reduces the cam pin slamming when the carrier moves backwards. Without the gas rings, the bolt is 'loose' in the carrier and the cam pin can slam against the front and rear of the cam pin slot in the bolt carrier during the cycle.

At the range, I did a quick 50 yd zero sight-in with a bipod in the prone position, and was ready to shoot. Accuracy was more than adequate to dial in the T-1 and iron sights. The rear iron sight was in the center when sighted in, not offset to one side on the receiver, which indicated receiver, barrel and gas block were properly lined up and nothing was canted or off.
Over the course of the day, I put 400 round through it; 300 rounds of Wolf military classic and 100 rounds of Prvi Partisan. I used the same lower that I usually do, with an extra power buffer spring from Sprinco/Tactical Springs and an Enidine buffer. The carrier locked back on the last round with both types of ammo, so the gas port looked like it was the right size. When building this upper, Chris had asked me what type of ammo I'd be shooting, and I told him 'just about anything - from Radway Green or Wolf to military M855 and 75 gr bullets', so he made sure that the gas port was sized to cycle the gun even with the slightly underpowered ammo.
Just like the PWS mid length upper, I could really feel no difference in recoil impulse between the Addax GPU piston upper and a DI upper - it's less harsh than a LWRC or HK416, and relatively soft shooting. The Addax Bulldog also functions the same as the PWS FSC556, keeping the muzzle jump to almost nil for quicker follow-up shots. The day was a lot of fun, running different drills, but as far as issues with the GPU, it was uneventful. No failures to feed, eject, or malfunctions of any kind. Here are some observations afterwards:

  • As expected, the bolt and carrier stayed cooler than that of a DI gun.
  • On the previous PWS upper, after the shooting session, when it got dirty, the gas adjustment knob was difficult to turn by hand due to carbon buildup, and required a 9/16" open end wrench to rotate it for removal. The ion bond on the components seemed to work, as well as the slight change in design on the piston tube, as I could rotate the knob and remove it without tools after the shooting session.
  • The gas piston still will not fall out freely out of the piston tube due to carbon build up, which is now something I expect, and I pushed it out by inserting the operating rod through the back of the gas piston tube, which is the recommend procedure according to the Addax/PWS user manual. PWS says the piston should be run dry, or very lightly lubricated at most. I wiped off the excess lube on the piston before shooting it - essentially 'dry', and that seems to work well to keep carbon build up to a minimum. If you read manuals for other rifles like the FN FAL or M1A, they recommend the gas piston and gas cylinder are to be run dry without lube, or else the lube bakes on with the heat and pressure.
  • I examined the top bearing surfaces of the bolt carrier for signs of carrier tilt and I don't see any - the round count is too low to tell. No wear at the rear of the carrier and inside the receiver extension either. I was very surprised to see no receiver wear at all from the cam pin. On my PWS upper, the cam pin wore the finish off the inside of the receiver just behind the cam pin relief cut, and has worn a small groove in that area. It seems that the wear has stopped at this point. On my other DI uppers, that place will always start wearing as well, then reach a point where there's no additional wear as the parts break in. On the Addax GPU, that area looks unmarked after 400 rounds. Usually I'll see some wear starting but there isn't even any finish wear.
  • The ion bonded components are easier to clean than the parkerized ones. I still had to soak the piston in carbon cutter to get the carbon off, but I didn't really bother getting it completely clean. Carbon residue wiped off the other components quite easily with solvent. For storage, I lubed all the piston components and assembled them wet, as I've found Wolf ammo to leave some residue. Before the next range trip, I'll wipe them dry.

Ever since the PWS piston conversion system came out, PWS has been working with dealers and evaluators like Addax Tactical to refine and improve the system. It has had its share of technical challenges, as have all the AR-15 based piston conversions. Is it a better mousetrap? Only time will tell. I've mentioned what I thought the advantages of a piston system are for the non-military shooter who doesn't fire SBRs on full-auto: the piston does get dirty with carbon buildup, but it's a lot easier to clean than the back of a bolt. The inside of the receiver, bolt and carrier also remain much cleaner. If you're a person that cleans your rifle every time you shoot it, I'd say that the piston upper IS easier and quicker to clean than a DI one. The bolt and carrier stay cooler and lube applied on the operating parts stays there and does not burn off.

If you've made up your mind and want a PWS piston system, I'd recommend a fully-assembled and tested upper like the Addax GPU over doing a conversion on an existing upper. With the Addax GPU series, Addax Tactical offers a good selection of very well put together uppers with some custom features using quality components with attention to detail and a growing reputation for excellent customer service and support.

Spike's Tactical ST-22 Upper

10/15/08 - The Spike's Tactical ST-22 Upper is a complete drop-on .22LR upper receiver for any AR15-type rifle, converting it to shoot inexpensive .22LR ammunition. Whether it's for fun, plinking or training, a conversion upper for an AR15 is quickly becoming a popular accessory for AR owners out there.

With today's ammo prices going up like gas prices, .223 has gone from less than 15 cents per round to over 30, 40 even over 50 cents per round. That case of XM193 that used to cost $150 is now over $400 if you can find it. Even the cheapest Wolf .223 that used to cost $99 per case is in the mid $200's at the time of this writing. Depending on the ammunition, .22LR can be had be less than $2 per box of 50 for the cheapest stuff, and even the decent stuff is about $3 per box of 50. My favourite .22LR ammunition, CCI Mini-mags are about $30 for 500 - only $60 per thousand. Compare that to $300-$400 per thousand for .223 and you can see the potential savings if you shoot a lot.

Besides cost, another advantage to owning a .22LR upper is that some indoor ranges do not allow centerfire rifle ammunition, only pistol and rimfire. I have to drive about an hour to a range that allows rifle ammo, but I have an indoor pistol range ten minutes from my house. It's very convenient and I get to shoot my AR when I otherwise might not have the time to go to an outdoor range.

Of course, .22LR has its limitations. It has pretty much zero recoil, and reduced report and power. Shoot it at steel and you might not hear the impact, let alone drop a plate. But it still makes .22 caliber-sized holes, and paper targets don't know the difference. Where I find a .22 useful is for basic marksmanship and drills under 50 yards - like practicing bringing the rifle up, acquiring the sights and pressing off a shot, or learning how to shoot on the move. When it comes to the argument about .22LR not recoiling enough - that happens after the bullet has left the barrel. The first shot is the same, whether it be .22LR or .223. The difference is in the speed of the follow-up shots; at least for the novice/unskilled person like me. I feel that shooting a .22LR AR15 helps make me a better shooter with a .223 upper as I can practice the basics more often.

Why get a conversion for an AR15 and not just get a Ruger 10/22? Well, you can set up your .22LR upper the same way as your other AR15s. Familiarity of controls, ergonomics, drills etc. Plus it's just a LOT of fun to shoot a .22LR AR. More so than a 10/22 in my opinion.
To shoot .22LR through an AR15, you can either get a conversion kit, or replace the entire upper. Conversion kits have been around for a long time; I remember the old Colt conversion kit with the plastic mag 20 years ago or more. These usually consist of a replacement bolt assembly and magazine. The bolt assembly replaces the entire AR15 bolt carrier assembly, and includes an attached chamber insert which 'fills up' the .223 chamber that allows .22LR to be fired through a .223 upper. Examples of popular conversion kits are the Ciener and USGI M261 - all are blowback operated. One of the problems with shooting .22LR through a .223 barrel is that the twist rate is not be optimized for the slower, lighter .22LR bullets which is usually 1 in 16. Nowadays, most people are shooting twist rates under 1 in 9 in their ARs.

The other option is to replace the AR15 upper with a dedicated .22LR upper like the ST-22.

My first Spike's .22LR upper

When I finally decided to get a .22LR upper for my AR15, I looked around and found that Spike's Tactical was often mentioned along with .22LR uppers. They used modified Ciener kits with dedicated .22LR Shaw barrels. All I really needed was an upper without the hand guards, as I was going to install my own hand guard on it. I purchased a Spike's .22LR M4 upper in October 2007, which had an A3 flat top with 16" 1/16 twist rate .22LR Shaw barrel with M4 profile. I also got the full size Black Dog Machine (BDM) 27-round magazines as I wanted to use the same pouches as my AR mags and I liked the look of the full size mags vs. the skinny ones. Customer service from Angela was excellent - friendly and accommodating. In a few weeks, I had my Spike's upper in hand. I set up my upper with a Vltor CAS-V hand guard, 'inexpensive' SPOT red dot sight, and spare parts that I had in my bin like a PRI front sight and GG&G MAD rear.

When I first loaded up the mags with the recommended ammo, pulled back and released the charging handle, the rounds would not feed at all. The bullet tip kept getting caught on the upper edge of the chamber. I had to remove the mag and shake the round out as it wouldn't eject (since it was jammed up at the top). The bullet was deformed and bent. I was pissed and disappointed. I had heard that the uppers required a 'break-in' period but how the would I break it in if I couldn't even chamber a round? Rather than send it back, I fixed it myself. I'm an engineer, and sometimes would rather do things myself than go through the hassle of sending it out, waiting, then getting it back. I smoothed the top edge of the chamber and also polished the feed ramp. I rounded the entrance to the chamber with a craytex tip. This did the trick, and all the rounds hand-cycled without hanging up. I also polished the rails on which the bolt cycled - the surface wasn't very smooth. At the range, the upper ran very well - feeding a mixture of all the .22LR ammunition I had. Spike's recommends only plated ammo in their upper. Through a thread on one of the forums, I also found out that others had experienced similar issues, and had to resort to similar fixes.

Now, I had fixed the feeding issue, but noticed another. I could not shoot this upper with acceptable accuracy, no matter what ammo I tried. When sighting in and shooting from a bench a 25 yds, using a bipod and rear rest, I expected it to shoot like my Ruger 10/22 - pretty much one-hole groups at that distance. Instead, I couldn't get anything better than 3"- 4". I checked everything - both the red dot and iron sights, ammo etc. I was disappointed for the second time. I chalked it up to 'eh, it's a .22LR - what do you expect?' and just sucked it up.

Even with the initial feeding issue and disappointing accuracy, this upper was still a blast to shoot. For 25 yards and under, it was adequate for most of the close range drills we performed at the range where there was a lot of moving and quick shooting. I just wouldn't be making many A zone hits on the head of an IPSC target. For shooting steel targets, and just fun plinking, it couldn't be beat. It was so nice to go through magazines of ammo with abandon, and not think about how much .223 I had in reserves. Just about everyone who shot it liked it, just for the sheer fun of it. So, this is how it went for a while, and I went through a couple of thousand trouble-free rounds (except for a few ammo-related duds) in a few range sessions, until I noticed a new person representing Spike's Tactical on the AR15.com forum.

Contacting Spikes

In early 2008, I had noticed an increased presence on AR15.com by a Spike's representative, Tom, who now ran the .22 department. He spoke about how changes were being made and improvements to their uppers were in work. A newly designed bolt and more barrel options. Also available was a barrel upgrade from the Shaw to the excellent Lothar Walther-manufactured barrel (they make the barrels for LaRue's Stealth Sniper System reviewed above). I contacted him, and described my negative experience with my Spike's upper.

Tom was very forthright, and said that there there had been issues with some of the earlier Spike's .22 uppers before his time. The Ciener kits were hit and miss - some worked well and others didn't. The old barrels also had issues with tight chambers, and were turned on a manual lathe. Tom was hired to head up the .22 department at Spike's, and they now use a CNC lathe and 4-axis CNC mill, and did a lot of R&D and testing to ensure that the new product would be a good one. All of the uppers are tested before they're sent out. If it doesn't run, it doesn't go out. Barrels that don't perform are scrapped. Tom will warranty any of the old ones like mine that have problems that are clearly due to the upper - either fix it or replace it, as customer satisfaction is very important to him. Of course, when it comes to accuracy, the shooter should be 100% sure it's not himself instead of the upper.
Anyways, I took him up on the warranty and sent back my upper.

The New Spike's upper

When I got back my upper, nothing of the old one remained. It had a new Spike's marked upper receiver and a Lothar Walther barrel (an upgrade I requested). Overall quality looked excellent. All new Shaw barrels are checked to make sure they are in spec - bad ones are scrapped. Some are barrel blanks turned on Spike's CNC machines and others are bought from M1S. The Lothar Walther barrels are available as an upgrade option, and Tom says that the LW barrels are the best .22LR barrels he's shot. Most of the changes have been to the bolt, which is based on the Atchisson design. Some of the changes made to the new ST-22 bolt are:

  • Electroless nickel plating - this finish requires no lube, which makes for a cleaner weapon and easier cleanup. Oil and .22LR residue creates a sticky mess in most .22s. Much less so with the nickel plating. The finish is also slicker and smoother so no polishing is required.
  • The bolt, rail, firing pin, extractor, spring guide etc are all made from improved materials. High quality tool steel is used where needed and parts are hardened.
  • Firing pin retaining pin relocated
  • Chamber adapter redesigned to raise the feed ramp and change the angle - the Ceiner was too low.
  • Recoil spring guide redesigned with an E-clip, and the rail was also redesigned with a pocket to accept a new spring guide.
  • End cap weld is now stronger and welded on the top and bottom instead of the back for a cleaner look.
  • Quality springs used throughout.
  • Bolt and rail designed to accept a ball and spring, which is part of the anti-bounce for full-auto.

The bolt assembly is easily disassembled into its main components for cleaning. Pull the bolt back, spread one rail enough to pop it out of its groove in the breech adapter, and rotate the breech adapter out.

ST-22 upper with my sights

Lothar Walther Barrel

New bolt assembly

Description - The photos above and below illustrate the Spike's Tactical ST-22. Spike offers a variety of configurations; different barrel lengths, sight and hand guard combinations. The one shown here is the M4-style with the PRI gas block I supplied. The Lothar Walther barrel is 16", but it extends back into the receiver about 1.5" giving it the look of a 14.5" M4 barrel. It has a 1x16 twist rate. The barrel has the standard AR thread of 1/2 x 28 and is very nicely machined. I noticed that there were no sharp edges around the chamber entrance.
The .22LR bolt assembly slides into the rear of the receiver, just like the normal AR bolt carrier. Only the bolt reciprocates on the rails; the entire assembly does not move back into the buffer tube. The front breech adapter with feed ramp slides over the rear of the barrel extending into the receiver. The end cap prevents any rearward movement of the assembly and fits flush to the rear of the upper receiver. The upper receiver is nicely laser etched on the left side with Spike's markings. The forward assist is there, but non-functional with the .22LR bolt, of course.

Bolt partially inserted into receiver

Markings on receiver

Bottom view

End cap

Shown below is my upper with everything reinstalled. All that is needed to shoot it is pop it on a lower, load up some BDM mags, and that's it. A note about BDM smoke magazines - DO NOT EXPOSE THEM TO SOLVENTS!!! - I took them apart and sprayed some dry lube on them, and they developed cracks throughout. There's a warning on the BDM site that should be (but is not) displayed on all their dealer sites. Instead of throwing them all away, I spray painted the ones that didn't have pieces break off with krylon khaki paint to cover up the cracks, and they didn't seem to develop additional cracks, so I'll use them till those fall apart. Inspired by my Magpul PMAGs, I masked off a small window when painting them - they actually turned out quite nice. I found some old Magpuls and put them on the bottom to further protect them if dropped onto concrete.

My upper setup

My painted BDM mags

Initial Range Report - I couldn't wait to try it out and went to an indoor range the day after receiving it. I ran the bolt without lubrication, except for a drop of oil on each rail, as recommended by Spike's. Shooting it dry helps prevent the dirty .22LR ammo from forming that gunk that gums up most .22's after a while. I went to an indoor range near my house, which is only 15 yards. Good enough for an initial function and sight-in. I started out with Federal Bulk Pack ammo; 150 rounds loaded into 6 mags. The lanes don't have tables; they have that plastic 'tray' at the booth where you set you stuff down on. Not very stable as a rest, but it'd do. I rested my elbows on it and sighted the rifle in. Much to my relief and delight, it was much more accurate than my first Spike's upper. I was getting groups around 1", which I found perfectly adequate for adjusting the red dot sight in, and pretty good considering the circumstances.

I did experience about a dozen failures to fire (duds) with the Federal Bulk Pack. All I'd get would be a 'click', then I'd eject the round manually and set it aside. Firing pin strikes looked normal. I loaded all the duds into a mag to see if they're fire when put through a second time. Only one did. I loaded and fired off 100 more rounds each of CCI Minimags and Winchester hi-velocity, this time with no duds or problems. The CCI Minimags have a little kick to them. Very cute.

I shot a series of 10-12 shot groups on the target shown below, again with my elbows resting on the tray and firing about 1 shot per second. All groups are around an inch. Granted, it was only 15 yards but given the circumstances, I'm very pleased with the accuracy potential that this shows. I look forward to shooting off a bench with a front and rear rest, or bipod, with various types of ammo.

After 350 rounds

Cleaning the rifle was almost a pleasure, as the residue was so easy to remove. Without lube to mix with unburnt powder and carbon, combined with the slick surface of the electroless nickel plating, the upper stayed cleaner than it normally would with oil. With the old upper and bolt, I had to run it well lubed, which created a lot of gunk after a range session. The photos above show it after my range session before I wiped most of it off with solvent and a rag. Any baked on residue was easily brushed off with a bronze brush. I ran a bore snake through the barrel a few times and called it day.

So far, this new ST-22 exhibits none of the problems with feeding or accuracy that the old upper did, and I'm very happy with the way it's performing. Kudos to Tom at Spikes for standing behind their products, old and new. I'll be updating this write up when I put more rounds through it.

11/8/08 - Went through another 300 rounds at the range, going through some drills. I ran through 12 mags of 25 rounds, first loaded with Federal bulk pack, then CCI Minimags. Only the Federal bulk pack ammo gave me problems. No feeding or extraction problems, just some duds. Maybe two per mag. The 6 mags with CCI Minimags ran through the upper without any problems - I think I'll keep buying CCI Minimags. I noticed more interest in .22LR uppers for cheap training from the guys I was shooting with. Cost, plus the pure fun of shooting one is making them more and more attractive for gun owners.

11/28/08 - Shot the ST-22 at 50 yds yesterday using a bipod off a bench, and magnified optic. I brought along four types of ammo, and show one of the representative targets below:

A - SK Pistol Match Special made by Lapua, 40 gr lead round nose. 10 rounds, group 0.63" (not counting the flyer on the left).
B - Aguila Match Rifle 40 gr lead round nose. 9 rounds, group 1.1". One dud didn't fire.
C - CCI Mini-Mags 40 gr plated lead RN. 9 rounds, group 2.9".
D - American Eagle 38 gr hollow point plated. 12 rounds, group 1.9". Smallest 10-round group 1.1".

The SK pistol match did best, with CCI Mini mags doing the worst. I was surprised that the CCI Mini Mags didn't shoot tighter, but they function the most consistently for me. I bought the American Eagle on sale so it was very cheap, and I'm pleasantly surprised to see it shoot better than the Mini Mags. Most of the shooting I do with the ST-22 is under 50 yards; mostly drills, so it's more important to me to have reliability vs. more accuracy at those distances. So far, the CCI Mini Mags have the least amount of duds (if any). But if I want to do some more precise plinking, I'd pick one of the other three types I tried. I'm happy to see that with the right ammo, the ST-22 has proven to be quite a tack driver at 50 yards.

1/3/09 - I've about 2500 rounds through the new ST-22 upper now, and last week at the range the small 'e-clip' on the rear of the spring guide rod broke, making the gun stop, and jam up the recoil spring. Spike's is sending out a replacement, and I'm thinking of using an o-ring around the rear of the recoil spring to act as a mini shock buff. Ideally, the shock buff should be flat and larger (see the red shaded area in the photo below), but I'll give the o-ring a try. Tom said that it's not a common occurance, but it it becomes more common, they'll look into a change. Also shown below is the ST-22 with new Vltor CASV-S bi-level rail and Spike's SD1 6" fake can to give it an 'SD' look. The SD1 adds no length to the barrel and replaces the flash hider. It's completely hollow (open at the rear). I got it from ADDAX Tactical.

2/7/09 - I initially put 400 rounds through the upper with the O-ring in place, with little visible wear on the O-ring upon inspection. I'll kept it in there to see how long it lasted, since it didn't seem to hurt anything. At another range session, I put another 450 rounds through the upper and the O-ring has flattened out some and needs replacing soon. So, I'd estimate that the O-ring lasts about 1000 rounds before replacing is needed.

I also did another mod to the ST-22. I'm a left-handed shooter, and with regular AR15s, have never had any problems with cases hitting me in the face etc. Since the ST-22 is blowback operated, I'll occasionally get some particles/unburnt powder coming out of the chamber with the extracted case and peppering me in the face when I'm shooting it. Not a big deal at all, but I saw an ST-22 built with a 9mm upper with case deflector, and I thought that'd be perfect to deflect the particles. 9mm flat top uppers usually have no forward assist and the case deflector, with a shortened ejection port door. But, rather than buy a whole new upper receiver to replace this one, I saw that Rock River Arms offered a 9mm case deflector and 9mm ejection port door. This can be installed on any flat top upper, as the 9mm case deflector doesn't interfere with the one already there behind the ejection port. I had to file a bit off the top to make it fit with my Vltor CASV handguard since it mounts on the top rail, but installation was as simple as replacing the ejection port door. Tom at Spikes had told me that sometimes the case deflector can cause an empty to bounce back into the ejection port and cause a jam, but I've got almost 1000 rounds through it with the case deflector and it hasn't happened yet. It definitely works to keep my face from being peppered with blowback particles and for only about $20, well worthit and I'd highly recommend it for lefties like me.

11/4/09 - At around the 4000 round mark, the firing pin broke and Spike's sent out a replacement. Also, they introduced their new one-piece guide rod, which replaces the one with the e-clip. The rear of the new rod has a solid 'ring' around it, with no e-clip to break. It's available for less than $10 to replace existing rods, and all new conversion kits will use it.





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