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.

Sight picture with large aperture (sighted in at 50 yds)

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 sight/leaf spring.
The FastFire is mounted directly to the base, and is protected by an arched aluminum shroud that has access holes for the windage adjustment screw and on/off switch on the left. Total weight is less than 3.5 oz.

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.

View through sight

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.

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.

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.

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)

• Size - the 551 is small and compact. Nothing protruding, very clean lines. I like it :-)
• Mounting system - None needed for the Eotech - it clamps right onto a pic rail. Aimpoint - you need a mount.
• Reticle - I like the circle/dot of the 551 better than the Aimpoint. The reticle was also clearer.
• Speed - Putting the 551's circle on COM was faster than the Aimpoint
• Height - The 551 sits a bit low on the flattop, so I thought I'd put it on the SIR. No go, as it won't co-witness with the iron sights - it's too high unless mounted on the front of the bi-level rail. The Aimpoint will co-witness on both RIS and SIR.
• Field of view - That's obvious - the 551's open window beats out any tube.
• Switch - The new 551 rubber buttons are great, but not as fast to turn on as the Aimpoint. With the Aimpoint, you just turn the knob. Not really much of an issue, but I wish the 551 'remembered' the last setting that it was at and turns on to the same setting. I'll probably get some flak for that. The 551 switch is also less likely to turn on accidently, something that the Aimpoint is notorious for.
• Auto-off - The 551 turns off at 4 or 8 hours. The Aimpoint doesn't have an auto-off feature, I've run a few batteries down as I left the AImpoint on at the highest setting.
• Reflection - The lens of the Aimpoint is very reflective, which is why the ARD has to be used. The 551 doesn't need one.
• Battery life - The Aimpoint has better battery life than the 551, but you can also get the 552 that takes AA batteries for longer battery life. But you give up a bit in compactness.

Overall, it's a toss-up. They're both good sights - and either should fit more shooter's needs.