Optics and Accessories Page 2
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Battle Arms Development Bracket and Screw for MATECH BUIS
2/13/10 - Battle Arms Development (BAD) is offering an improved Bracket and Screw set that replaces the original bracket and screw on the issue Matech B.U.I.S. It features a thicker and stronger bracket and a stronger screw with smaller Allen head socket to minimize over-torquing.
Description - The original Matech mounting screw has been known to snap from overtorquing (from users not reading the included manual) as it has a large head and thin body. The screw that BAD selected has a smaller head to minimize the possibility of over-torquing and is a stronger, grade 9 plus screw.
The bracket has been redesigned with a re-aligned screw hole to minimize canting of the screw and bracket. It has more contact with the sight than than the factory clamp and the gap that exists between the top of clamp and the sight is practically eliminated. The additional thickness of the bracket allows the head of the screw to be partially recessed into it. The bracket is CNC'd out of steel, not cast or MIM'd, and finished in black phosphate.
Insight Tech-Gear MRDS
9/25/09 - The MRDS (Mini Red Dot Sight) from Insight Tech-Gear is a non-magnified, light weight, ruggedized reflex weapon sight intended to be used as a stand-alone primary sight, or as a secondary/backup sighting device in addition to a primary optic. It mounts to existing optics as well as MIL-STD 1913 Picatinny and Weaver-style rails, utilizing available aftermarket mounts. It is designed to meet and exceed military durability specifications for equipment used by special operations personnel under combat conditions. Insight Tech-Gear is a leading provider to tactical lasers, illuminators and thermal imaging equipment to the military.
Background - Many shooters should now be familiar with mini red dot sights. I think the first one that came out was the now-discontinued Tasco Optima 2000, designed by the British Firepoint company. I still have one mounted as a backup to a magnified optic. It was tiny, compared to other red dot sights, and was likened to the C-More Serendipity. The Serendipity differed from other red dot sights by the fact that it was tubeless. It had an open lens, on to which a red dot was projected. Same principle as other red dots, only there was no tube surrounding the lens. The Optima 2000 was essentially a miniaturized version, and smaller than anyone had seen before. They were popular on pistols due to their tiny size and light weight, but also found their way onto rifles and shotguns. The Optima 2000 was discontinued, and is now manufactured by JPoint. My second mini RDS was a DOCTER optic - a higher quality version of the Optima 2000 (in my opinion). Others came out in the following years, like the Pride-Fowler and Burris FastFire.
Mini red dots started showing up piggybacked on the ACOG a few years back as a close quarters alternative to the 4x scope. I mounted my Optima on top of my TA01NSN, and while it worked, I didn't find it optimal due to the 'chin weld' position and large offset from the bore. I switched over to an offset angle mount which placed the mini red dot closer to the bore and found that it worked much better for me, as all I needed to do was cant the rifle slightly. Mounted to the rail instead of on top of the optic, it was less exposed to knocks and bumps.
Whether or not to use mini red dots as a primary or secondary optic will depend on the user's needs. The argument against using an MRDS as a primary sight is that while ruggedized (as far as a mini red dot goes), it still has an exposed LED emitter/open lens configuration, that isn't as easy to clean or clear if mud happens to fill up the recess behind the lens as a tube design. With a tube design, the mud can be cleared more easily from the lens, and even so, only the rear lens needs to be cleared of obstructions (you can still use it as an OEG with the front lens occluded). This might be just an inconvenience to the civilian user, but more serious for the military user. As a secondary, the MRDS can be kept covered until needed, but as a primary, it'd most likely be uncovered all the time.
That being said, this write up isn't meant to recommend what's best for your needs, but to provide the reader with information so he can decide for himself. As far as mini red dots go, the Insight MRDS is one of the newest generation mini red dot sights, which incorporates some of the better features from each of its predecessors in a more durable package for military use.
Description - The MRDS is available in four variants; users have the choice of two dot sizes (3.5 or 7.0 MOA) and housing colours (tan or black). Note that the MRDS is normally sold as a basic package, which does not include some of the accessories shown here. The basic package does not include a mount or protective hard shield - those are options and are sold separately. At the time of this writing, Insight-Tech is still determining whether a basic weaver mount should be included (either of their own manufacture or aftermarket), or left up to the user to get separately, as the mount is wasted if the MRDS is mounted on an ACOG or magnified optic. The DOCTER is sold the same way - sight only, no mount.
The MRDS housing is molded from advance polymers reducing weight without sacrificing operational durability. The lens is impact-resistant polymer with a proprietary abrasion-resistant and anti-reflective coating. Insight put the MRDS through a variety of tests, which include water and salt fog testing, freezing in ice, drop testing, vibration/shock, and shot on various weapons for thousands of rounds. The MRDS passes the MIL-STD 810G environmental testing protocols.
The MRDS comes in a typical Insight plastic box, with foam cutouts. A soft cover, mini lens cleaning pen, operator manual and laminated quick reference guide are also included. The military kit is shown below with the protective shroud shown which is not included in the basic kit. The polymer housing is devoid of sharp edges and looks to be quite sturdy - much more so than the Tasco Optima 2000, which also had a polymer body. The battery compartment is accessed via a hinged lid on top of the housing, which is o-ring sealed, and secured with two small captured slotted screws. This eliminates having to remove the sight from the base to replace the battery, allowing it to remain zeroed. Rather than the CR2032 coin battery used by the Docter, FastFire or Optima sights, the MRDS uses the smaller CR1632 coin battery which the Pride-Fowler also uses. These are readily available at most drug stores for a few bucks, or cheaper online for about $1 a piece. The battery allows the unit to operate for about a year in Auto mode.
On the front of the housing under the lens is the photo diode/light sensor. This senses the amount of ambient light hitting the front of the sight and adjusts the dot brightness automatically. The elevation adjustment screw is on the top, and the windage adjustment screw is on the left side of the housing. A low profile push-button membrane switch is at the rear of the housing.
Installation - The MRDS is shown below with a prototype Insight mount, and the aluminum protective shroud; both not included in the base package. The mount, which Insight manufactured themselves upon request by a military customer, proved too expensive, which is why they're currently looking to source a base elsewhere. The base has four steel studs that interface with holes in the base of the MRDS, preventing it from moving on the base when installed with the two screws. The soft cover protects the MRDS from dust when not in use, and has a small tab for dummy cording it.
The aluminum protective shield is intended for military use. Under normal civilian use, it's not really needed. When installed, the aluminum protective shield/shroud encloses the lens, and the forward half of the body. It follows the lines of the sight very closely so it doesn't add much noticeable bulk. It is installed with longer screws (10mm vs. 8mm) between the MRDS and the mount. The locating studs in the mount protrude through the shield, and into the base of the MRDS. The shield will also work with DOCTER mounts. The shield can be ordered from Insight through their distributors. The soft cover isn't designed to fit over the shield, but I found that it would stretch over and work. Not perfectly, but it'll still work in a pinch.
The MRDS is shown below mounted on a Vltor CASV, and M4 flat top. I found the Insight mount to be too high to co-witness properly with the CASV, and a bit too low for the M4 flat top. In a perfect world, I'd have liked the mount to come in two parts - a lower profile one for CASV mounting, and a spacer for flat tops. Other than that, installation was straightforward and simple.
Operation - The MRDS is operated using the small push button at the rear of the housing. Pressing it for less than one second turns it on. The default mode is Auto Gain when you first turn it on. With the MRDS turned on, each press of the button sequentially steps it through each mode of operation.
The elevation and windage adjusters are moved using a small flat head screwdriver, and have tactile clicks. Each click moves the point of impact 1 MOA. The direction of the arrows molded into the housing indicate the movement of the group/point of impact.
Observation and Notes - Upon examination, the MRDS looks like a high quality optic. All assembly screws are sealed/bonded over. When I first mounted up the MRDS on my rifles, I tried it out on both a flat top and rifle with Vltor CASV. As I mentioned above, the Insight mount was either a bit too low (on the M4) or too high (on the CASV), and I'd have liked something that worked for either a bit better, for co-witnessing. I ended up putting it on the M4 (actually the Addax Tactical ATAC gas piston upper which I'm still putting rounds through for testing), and used it at the next range session. I initially adjusted the dot to co-witness with the irons at home to get it close, then adjusted it when I got to the range. The click adjustments were a easy to use with a small screwdriver. Each click was very positive. All of my other mini red dot sights have non-click adjustments, and set screws which lock the adjustments in place. I dislike set screws, simply because they can damage the threads of the adjustment screws over time. Also, once a flat spot develops on the thread, tightening the set screw can sometimes move the screw (and dot) a bit. With the MRDS, adjustments are quicker and easier without having to loosen and tighten locking set screws. I got it sighted in quickly with the minimum of fuss.
The push button is very low profile, and doesn't provide any tactile feedback. I have to be looking through the sight to see if my presses are taking effect. Initially, I found it a bit difficult to press, and I was using my fingernail, but after a bit, it seemed to be easier to press, and I can make adjustments using the tip of my thumb, not the fingernail. Using gloves is possible - I tried it with two different pairs of shooting gloves and was able to actuate the button. Thicker gloves might prove more of a problem. I'd prefer a slightly higher profile push button with some kind of positive feedback, so you can tell when you're pressing it in.
I like having an on/off switch and the option to adjust dot brightness manually. The Optima and DOCTER don't have any controls, and depend on their covers to turn them 'off'. They don't actually turn off, but go to a very low level in the auto setting in the absence of light. I stepped on and broke my DOCTER cover soon after getting it, and had to get a new one, and would prefer not need one. The FastFire only has auto/off, and the Pride-Fowler has off, auto and max brightness settings.
The lens of the MRDS has a very faint bluish tint - essentially unnoticeable when you're using it - and less noticeable than the tint on the FastFire or an Aimpoint T1. Optical quality of the polymer lens is excellent. Max dot brightness is brighter than the DOCTER and a not quite as bright as the FastFire, and I had no problems seeing it in bright sunlight against both light and dark targets. I left it in Auto Gain mode the whole day, and didn't have to make any adjustments.
The sight picture isn't much different from the other mini red dot sights, and I wouldn't expect it to be. Other than subtle differences in dot intensity, lens clarity or dot size, the MRDS will be familiar to users who have mini red dot sights. Since there's no tube, there's very little blocking the field of view. I don't notice any distortion through the lens.
Changed the mount - As I mentioned before, the Insight MRDS mount is too low for my liking on an M4 flat top, so I looked for an alternative. The LaRue irondot mount for the DOCTER or Burris Fast Fire is at the perfect height, but both of mine were in use already. I then remembered that I had a DOCTER set up on a shotgun, and that combination might work. I swapped mounts and put the Insight one on the shotgun with the DOCTER, where it actually worked better in that application. The replacement mount was made up of a LaRue LT-170 base with the rail taken from an A.R.M.S. #17DR, with a DOCTER weaver mount on top of it. The DOCTER weaver mount is lower than the Insight one, and placed on top of the LT-170 with DR rail, provides a good co-witness with full view of the iron sights through the MRDS lens window (see photo below). Yes, it's a bit convoluted, but it works well.
When compared to other mini red dots on the commercial market, the MSRP of $650 for the MRDS seems pretty high, but it's actually on par with the waterproof version of the DOCTER optic, which was a couple of hundred more than the standard version. However, I've seen the 'street' price substantially lower at various online retailers and about the same as the standard DOCTER optic (in some cases, even lower). Having owned the Optima, DOCTER and FastFire (and played with the Pride-Fowler), I'd put the MRDS at the top of the heap, as it's not only ruggedized, but offers the best dot brightness options and adjustment features. The MRDS is designed for military use, so hobbyist/enthusiast shooters who might not subject it to the environmental conditions to which it has been designed for might find it more than they need, like an ACOG vs a cheaper 4x scope. That's the difference between something designed for the commercial market and one for the military market, and it'll be up to the user to determine which one suits his individual needs the best.
Magpul Industries MBUS
4/24/09 - Magpul Industries has finally released their long awaited (at least for me, since SHOT 2008) MBUS (Magpul Back-Up Sight). What makes them different from other back-up iron sights? They're made of polymer, not iron. They were designed as a low-cost alternative to more expensive steel/aluminum front and rear sights, and a set of both front and rear cost as much as a 'iron' rear sight would. Being made of polymer, they can be produced in any standard colour Magpul manufactures their other products in. Shown here are the MBUS in flat dark earth.
Description - The front and rear MBUS are made up of three main parts each: the base, the release latch, and the flip-up sight. The front and rear share the same base and release latch, with the flipup portions differing. The flip-up portions are spring loaded and have two notches that retain them in the folded position. The notch is engaged by a hook, or tooth, on the release latch. When the latch is depressed (either by pressing down on the Magpul logo on top, or by using the serrated side extensions), the hook disengages the lock notch and the sight portion flips up instantly. The sight portion is held in the deployed position by spring tension, and is not locked by the release latch. If struck, they will collapse momentarily, then return to the deployed position. Pressing the sight portion back pushes the hook on the release latch down, out of the notch, and the sight portion can be stowed.
Front MBUS - The front sight has two protective ears that are slanted inwards at the top, rather than outwards like the standard M16 front sight, providing a sight picture much like the original Troy sights with the rounded ears. Being made of polymer, the ears are a bit thicker but I didn't find that to be an issue. The front uses a standard square front sight post, which can be adjusted with a 4-prong M16 sight adjustment tool. For each 1/4 rotation, the POI is moved approximately 1-7/8" at 100 meters, based on a 14.5" M4 sight radius. Once sighted in, the sight post can be prevented from rotating by installing a roll pin (two lengths are supplied) to lock it in place. I found the sight post very stiff to turn, so I didn't feel that it was necessary to use the roll pin.
Rear MBUS - The rear MBUS has a windage adjustment knob on the right side that adjusts the POI approximately 3/4" at 100 meters for each click. Both large and small apertures are provided; the small aperture flips forward out of the way, rather than rearward, and can be left down when stowing the sight.
Installation - The MBUS are installed onto a rail by removing the base cross screw and sliding them from the front or rear onto the rail. The screw is then reinstalled and tightened down. The polymer is slightly flexible so when the screw is tightened, the base clamps down on either side of the rail and is rock solid without any movement.
Observation and Notes - Being made of polymer, the MBUS are a bit bulkier than most other metal sights, which is not unexpected. That may or may not be an issue, depending on what kind of optics you're using (if you need clearance). I installed them on my LMT MRP and found that they are longer than most of my other sights, so they do take up more rail space. All I had to do was move my Aimpoint M4 and LaRue magnifier forward one notch on the rail. The MBUS are about 2.6" long while my Troys are about 2.2" long. The MBUS are about 0.7" at the highest point above the rail, and the Troys are 0.5".
So, while a bit higher profile than metal sights, the MBUS are featherweight and while I don't have a scale, they do feel lighter than metal sights when compared in the hand. I'm sure some will have concerns about the possibility of polymer sights cracking or breaking from impacts to hard surfaces or objects (such as banging them against a metal doorway when exiting a Humvee or something), so that remains to be answered in time after they've been out in the field there for a while. I'd expect them to perform like the other plastic parts on the rifle, like buttstock, pistol grip, vertical grip, rail covers, magazines etc.
When the release lever is pressed, the MBUS deploy instantly, and with a vengence. I preferred to deploy them by pressing down on the serrated side extensions, rather than pressing down on the top with the recommended quick 'karate chop' motion of the hand. If not wearing gloves during the chop, a bit of the knife edge of my hand could get pinched at the hinge between the release lever and the sight. In an emergency, of course, whatever works. That being said, deploying them by the side extensions was very easy, and for some strange reason - fun. I kept flipping them up just to do it the first time out at the range. I found them to be the most easily deployed back-up sights when wearing gloves because I didn't have to use a finger to lift them up, and it could be done on either side. Some other sights flip up just as quickly with a push of the button, but they're not ambidextrous and are more easily deployed accidentally (from contact with equipment or when setting the rifle down) than the MBUS mechanism (which requirse the downward pressure rather than a side push).
The one small thing that I'd change is to make the front sight a bit taller so that the front sight post isn't so high relative to the ears, and has less exposed thread. The front sight was probably made shorter so it wouldn't take up so much rail space, but I'd take another .1" to protect the front sight post more, just in case on some rifles it ends up higher than the top of the ears.
While there may not be a need to run out and replace your existing metal sights with the MBUS if you're happy with them, the MBUS are definitely worth considering when purchasing new sights as they're well designed, just look damn cool, function well and are on average less than half the cost of metal sights. And did I mention that they're fun to deploy? Kudos to Magpul for always trying out new things.
LaRue Tactical AK IronDot MRD
1/21/09 - LaRue Tactical listened to AK shooters expressing the need for a simple, low profile optic for the AK weapon and came up with their AK IronDot. It's a solidly-mounted mini-red dot sight (MRD) that replaces the rear iron sight on the AK, for the most compact red dot for the AK available yet.
When it comes to optics choices for AK-type weapons, the limiting factor is the lack of a good mounting surface on the top the weapon. The logical place for mounting an optic is top of the receiver on most rifles; but on the AK, the top of the receiver is the removable top cover, which was not designed for mounting any kind of optic. Various solutions include side-mounted receiver mounts, but not all AKs have provisions for those (mine doesn't), replacement top covers, and rails mounted to the gas piston tube (replacing the upper handguard). For the purpose of this writeup, we'll assume that we're referring to red dot sights, not magnified optics. Another challenge for mounting an optic on the AK is getting it low enough to be able to see the iron sights through the optic. When I was considering putting a red dot on my AK, the gas piston tube-mounted one seemed like the only one that would also allow the irons to be seen through an Aimpoint, but I just didn't feel that it was the best solution as a lot of heat could be transferred to the optic from that mounting position (the gas piston tube can get very hot). So, what's left on the rifle? Not much, but the rear sight block. And that's what LaRue went with.
Description - The rear leaf sight on the AK sits in
a mounting slot in the rear sight block which allows it to pivot for
elevation adjustments. The AK IronDot utilizes the rear sight block
as the mounting interface by replacing the stock rear iron leaf sight.
The IronDot base is machined from steel, and creates a low-mounted platform
for the Burris FastFire MRD optic (more on that later). The front of
the base emulates the stock rear sight, and has two pins that engage
the slot in the rear sight block. Two very strong magnets keep the mount
'stuck' to the top of the block, in addition to the replacement rear
Installation - Installation is very straightforward; the toughest task is removing the stock rear sight. Since I had tackled this task before when I replaced the stock rear with a Mojo ghost ring rear, it went a lot more smoothly this time and without the cussing and scraped knuckles of the first time. It helps if you have three hands, too. Anyway, after removing the rear sight, the leaf spring is left in place. This puts tension on the front of the base bar, and allows it to be pivoted up or down. The IronDot is installed in exactly the same way the stock rear is installed. The IronDot is fed in at a 45° angle while pushing forward in the slot against the tension of the leaf spring. Eventually, it pops up in place and the two pins on the base bar find their home at the top of the slot. The magnets pull it down and keep it against the top of the block. Next, the combination rear sight/leaf spring is placed on the corresponding notched pins on top of the bar and is then slid rearwards - all I need to do was tap it with a plastic mallet and it went in without an argument. Once in place, the rear sight/leaf spring presses down at the front and keeps the base locked in place. The base is rock solid and I can detect absolutely no movement.
The IronDot is supposed to be pivoted up to facilitate disassembly, but I did not have to do so to remove the top cover. Removing the rear sight/leaf spring is necessary on my rifle only if I have to remove the upper handguard/gas piston tube.
Burris FastFire - The AK IronDot is designed to be used with only the Burris FastFire right now, and will not work with other MRDs like the Docter or Pride Fowler. The FastFire is included in the price of the IronDot and comes installed to the base, ready to use. I've used the FastFire on other weapons and it's my current favourite of the MRDs I own, which are the Docter and the discontinued Optima. It costs less than the Docter and has a glass window, which provides better clarity than plastic ones like the Optima. While it automatically adjusts the dot intensity based on ambient light conditions, I like the fact that it also has an on-off switch, unlike the Docter. The Docter depends on the plastic cover to shut it down to a very low level to conserve battery power. The protective shroud prevents the use of this cover, which is one of the reasons why the FastFire is suited for this particular application. On the LaRue's AR-15 IronDots, the shroud is much less close fitting and allows the use of the plastic cover, but results in a higher profile.
The one caveat with the FastFire is that in darkness, the dot pulses (blinks rapidly). This can be a bit distracting in low light. Another is that the dot can be too faint to be seen if you're in a dark room looking out into a lighted room. This is because the intensity of the dot is governed by a light sensor on the front of the body; it's a small hole in the center right below the window (same thing applies to the Docter). The hole is partially obscured by the rear sight leaf and base so it doesn't get direct light from the front and depends on ambient light to adjust the intensity of the dot. So, take note if you plan on using the AK IronDot in low light that you may encounter this phenomenon. On the plus side, when looking out of a dark room into a bright one, the iron sights are clearly silhouetted and are perfectly usable.
I've used the FastFire on ARs and a shotgun, and have no complaints with it whatsoever under good ambient lighting conditions. It has a clear, bright 4 MOA dot (brighter than my Docter under the same lighting conditions), and utilizes the same CR 2032 coin battery as most other MRDs. Windage and elevation adjustments are accomplished by first loosening two locking set screws, then using the small supplied screwdriver to turn the windage screw on the side or elevation screw at the rear to move the dot. I've found that it's easier to sight in the irons first, then move the dot so that it sits right on top of the front sight post, rather than starting out with the dot adjustments first.
Observation and Notes - The AK IronDot is pretty much the most compact sighting option for the AK - I don't see how you could get smaller than this. I've attempted to show what the sight picture looks like in the left two photos below, but take note that the dot is focused at infinity, and is sharp and smaller to the eye than in the photos, which are focused more on the sight. The irons co-witness in the lower third of the Fastfire's window.
When I zeroed the IronDot at the range, I first adjusted the irons. No windage adjustment was necessary using the IronDot rear. It was centered perfectly, so I didn't have to drift the front sight. However, the rifle was shooting high with it. The rear sight is non-adjustable so all elevation adjustments have to be done with the front sight. I raised the front sight to lower the point of impact but it was still shooting high after I had raised the front as much as I was comfortable with. It was about 1/4" higher than its original height, and above the ears. The only solution is to lower the rear sight leaf, but I'm not sure how that can be done. I've an inquiry into LaRue about it. One explanation might be inconsistency between different AK types (mine is a Hungarian AK) of the height of the channel where the base sits on the rear sight block. The stock rear sight doesn't depend on it as the rear slide rides on the ramps on the sides. Adjusting the FastFire was a piece of cake. Once I knew where the rifle was shooting with the irons, I adjusted the dot, first in windage, then elevation, using the irons as a reference.
Shooting the AK with the IronDot is a joy, really. For me, a great improvement over the irons, and basically no change in cheek weld or position from using the irons. In the photos below, it was an overcast day (rainy) but ambient light was good and the dot was bright and clear. The AK IronDot is so lightweight that I couldn't discern any difference in weight. It's compact so it doesn't get in the way. One of the best things about it is how affordably priced it is ($285 which includes the FastFire). While an Aimpoint T-1 version of the AK IronDot might be the ultimate optic for the AK, it's going to cost more than some AKs out there. Even so, as the AK gains popularity, it makes sense to make mounts available for the higher end optics. For now, the LaRue AK IronDot with Burris Fast Fire is a great match for this weapon. For me, it makes it a lot more enjoyable to shoot.
Vltor VST-1C Folding Front Sight Assembly Torque test
7/30/07 - I previewed Vltor's VST-1C Folding Front Sight Assembly on the M4K and on the midlength VIS build, back in January '07 and they're now available. I've since installed another on an M4 barrel with carbine gas system and I really like them.
The question of the security of non-pinned gas blocks has been brought up numerous times. Factory-pinned front sight blocks have taper pins, which secure the gas block/front sight assembly to the barrel. Aftermarket gas blocks in general come in clamp on, and set screwed types. This is because it is next to impossible for the end user to re-drill taper pin holes in a blank gas block to match ones already present on a barrel. While taper pins can be installed in a blank gas block and new barrel, this is a gunsmith-only installation requiring the right tools and equipment. Set screws work by 'digging' into the surface of the barrel when tightened, or pre-drilled depressions or steps machined into the barrel. Barrels with these are still relatively uncommon, but available. If you look at the cross section of a gas block as a ring, set screws push the ring away from the barrel at the set screw locations. Normally, they draw the gas block down, to form a tight seal over the gas port. However, you have reduced surface area of contact - and a knock or torque to the gas block powerful enough to dent the metal underneath the set screw can possibly cause the gas block to loosen up. For that reason, set screw gas blocks are probably better left to low profile ones protected under a rail or handguard, rather than exposed ones with front sight towers.
Clamp-style gas blocks/front sights like the PRI and the Vltor have a split-ring cross section - there is a gap at the bottom of the clamp with two clamping screws that tighten the gas block around the barrel. This ensures maximum surface area contact between the gas block and the barrel. While theoretically not as secure as a taper-pinned gas block, I wonder if concerns about the security of clamp-style gas blocks are for the most part exaggerated. The split-ring clamp configuration is a very old, extremely secure design used in countless applications. Motorcycle triple clamps are one example - which secure the front forks to the steering head of the frame. And these are on very smooth polished surfaces, not relatively rough surfaces like a parkerized or bead blasted barrel. The key, as with all mechanical things, is proper installation (correct hardware torque and a clean surface) to prevent failure.
Additional security - The Vltor VST-1C has small divots on the gas block body to the side of each clamp screw ends. After installing the screws with high-temp non-permanent loctite and torquing them, the ends of the screws are center-punched/staked, which drives some of the screw's metal into the divots. This prevents any rotation and loosening of the clamp screws due to vibration or heat cycling. They can be removed with tools but will need to be replaced.
Still, I was curious how much torque or force it'd actually take to move a clamp-on gas block.
Torque Test - Since the Vltor VST-1C has provisions for a QD sling swivel, some people have brought up concerns that attaching a sling to the gas block might cause it to rotate, thereby rendering the weapon inoperable. I asked the guys at Vltor if they were willing to perform a test that would quantify the force needed to move/rotate one of their gas blocks and they were open to it. An impact test would simulate a sharp knock on the gas block, such as banging it against a metal door when exiting a vehicle. However, an impact test requires a specialized instrumented setup which was unavailable and is much more complicated to set up as there are so many more variables (what the gas block hits, how fast is it moving, how much weight if behind it etc). So we decided on a torque test, which was measurable and relatively easy to setup. This would provide a number which some enterprising individual might use for further calculations (not me) if they wanted to. We also wondered the sight block would move before damage to the barrel or receiver would happen.
The test, as performed and written up by Vltor is as follows:
Due to the failure of the barrel index pin and damage to the receiver at about 110 ft-lbs (1320 in-lbs) (actual was more than indicated setting on the torque wrench due to the moment arm length), it's inconclusive at what point the gas block would have rotated on the barrel. The distance of the sling cup to the centerline of the barrel is 0.6". This means that a force of more than 2200 lbs would have to be exerted on the sling to obtain similar results. For those who were worried that attaching a sling to a properly installed Vltor VSDT-1C would cause it to rotate, I think that worry can be put to rest. As far as impact to the gas block from dropping the weapon or smashing it against a rock or hard object, it's going to take a hard hit to move it, if at all. For those who still want a pinned-on gas block, Vltor will be making a taper-pin version in the future which will have to be gunsmith-installed.
Vltor VST Folding Front Sight Tower (Gen 2)
11/08/09 - I previewed Vltor's VST-1C (Vltor Sight Tower) Assembly on the M4K and on the midlength VIS build, back in January '07 and they've been available for a while now. A few months ago, Vltor updated the design with four different variations available.
Description - The Vltor Sight Towers are gas blocks that incorporate a folding front sight tower with an AK front sight post. It's an all-steel, flip-up design, with a spring loaded detent which keeps the sight tower stowed or deployed. The reason behind it not having a mechanical locking mechanism is that if impacted, the detent will allow the front sight tower to move, whereas a locking mechanism might be damaged or broken. The spring force has been greatly increased on the Gen 2 and the tower locks up or down much more positively than before. The front sight has also been lightened, with a thinner side profile and grooves on the sides for better purchase when deploying it. A square AK front sight post is used.
The entire gas block has been lightened, with a slightly trimmer look. The rail on top of the gas block has been retained. Four variations are available - with or without QD swivel cup mount, and clamped or pinned versions. The pinned versions have pilot hole locations for starting the taper drill. Installation by a qualified gunsmith is definitely recommended. Don't try to pin a gas block yourself without the proper tools/equipment.
|3/18/06 - Eotech's 553 (military version)
takes CR123 batteries which are now commonplace, for an advertised battery
life of 1100 hours at nominal setting. The two CR123 batteries are housed
in a battery compartment that is tethered to prevent loss. Finish is flat
dark earth, a USSOCOM colour (in which the Vltor and Tangodown furniture
below are available in as well). A great improvement over the single screw
mount of the previous versions are the A.R.M.S. throw levers. I don't
find them to be obtrusive in any way, on the left side. The 553 is also
about .25" higher than the 551. I found that the 551 sits a bit low
on a flattop, and adding a .25" riser gives the best cheek weld.
The 553 addresses that issue, and puts the window/reticle at the right
height now. It also co-witnesses the irons in the bottom 1/3 of the window
instead of centering it vertically, also an improvement.
The reticle is unchanged (to my eye), still the 65 MOA circle and 1 MOA dot. There are 20 brightness settings and 10 in night vision mode (activated by the center toggle button). Side signature has been eliminated by the use of internal anti-reflective coatings. Most other specs are the same as the others in the 550-series, which current Eotech users will already be familiar with.
ACOG/MRD mounting option
4/7/07 - Another trend that's developed over the years is to mount a mini-red dot (MRD) on top of the 4X Trijicon ACOG series scopes to provide close-range capability and speed that can be difficult with the magnified optic. Years ago, KAC came up with a mount that replaced the rear ghost ring on the TA01NSN ACOG, then in 2003, Specwargear came out with their own Doctor optic/Optima mounts (the SWG Optima mount is shown below). This was followed by JP and others. The drawback to this mounting position is that it's so high off the boreline that you don't get any cheek weld. At best, it's a chin weld. I've used it, and it worked decently for me. Since it was for close-range use, I sighted it in at 25 yds, but had to keep track of the offset/hold over for distances in that range if precision was needed (keeping head shots on targets in the little box).
A mounting option borrowed from the 3-gun match crowd is to mount the MRD on an offset angle mount. In 3-gun, in which targets can vary from CQB to medium distances, some competitors have mounted dot sights like the C-More at an angle on their tubular forend, in addition to their magnified main scope. To engage a target, the rifle is simply canted inward (the dot is mounted on the strong side) slightly and the cheek weld is maintained. It's no slower than moving your head up to look through an MRD mounted on top of the ACOG, and has less offset from the bore. Note that if you transition to the 'weak' shoulder, the rifle is now canted a bit outboard.
Shown here is a Docter Optic with its weaver mount, attached to a Yankee Hill Machine 5-slot dovetail angle mount, attached to the rail just forward of the ACOG. For $29, it's a very inexpensive option. This will also work with the Burris FastFire with its supplied weaver mount. The rifle only has to be canted about 10° to see the red dot. Note that I shoot left handed, which is why the MRD is on the left. It would be mounted to the right of the ACOG for a right-handed shooter. WIll it work better for you than a top-mounted MRD? That's up to you to decide, depending on your needs.
View Through Some Optics
This is a view of the ACOG mounted on the M4. The ghost ring sights are on top. GG&G MAD (Multiple Aperture Device) is folded.
Here's a view of the ACOG reticle. You can see the holdover lines for 100-600 yards. Zero is at 100 yards.
This is a view through the Aimpoint COMP M, showing the red dot. The ARMS rear sight is folded down out of the way.
Shooting impressions: The ACOG is suited better to ranges past 50 yards due to its 4X magnification. The ghost ring sights can be used for very close distances but they're not very precise due to the large rear aperture and using them requires you to break your stock weld as you have to look over the scope. The ACOG has very clear optics and is quite effective up to medium distances. The Aimpoint Comp M is great for CQB to medium ranges. It's an extremely fast sight to use, as both eyes are kept open and the red dot is superimposed on the target. One of its drawbacks is that it is battery powered and I've heard that they are not as durable as advertised, especially the switch. Electronics can fail, and they do. The Trijicon Reflex sight is nice and simple, needing no power source, but you have no control over the brightness of the dot, since it relies on ambient light and tritium. The Reflex dot can wash out if you are in a darkened area (indoors or shade) and you are looking at targets in bright sunlight. Same thing with the Tasco Optima. Try it and you'll see.
After shooting the Aimpoint Comp and the Eotech 551 side-by-side, I'm still undecided as to which I like better. I used the 551 in a carbine class, and it performed admirably. Then again, I've used the Aimpoint in a few more classes and that did just fine, too. When I took the Eotech to the range to sight it in, the dot was more distinct than the Aimpoint's, much to my surprise (for my vision). I like the circle/dot reticle for close ranges, you just center the circle on COM and that's it, or at very close ranges, use the bottom of the circle for hold over. The dot is also good for anything up to 300 yds. One thing - the 551 sits a bit low on a flattop so I thought of swapping it over to my SIR. That didn't work as I couldn't co-witness the iron sights; the 551 sat too high on the SIR. It stays on the flattop, and the Aimpoint goes on the SIR. You could also use some risers that raise the Eotech up so the irons are in the bottom third of the window.
MM quick-comparo (personal opinion)
Overall, it's a toss-up. They're both good sights - and either should fit more shooter's needs.
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