Back Up Iron Sight Drop Test

This is a guest post from Andrew Tuohy, a former Navy Corpsman and small-arms enthusiast. He wanted to see how three popular, rear back up iron sights performed after dropping them on concrete. The results are pretty interesting.

Here’s Andrew’s Review:

Back up iron sights, or BUIS, are a popular accessory for AR and M16/M4-platform rifles, with the primary reason for their purchase and use being that they offer a second method of aiming the rifle in the event that the primary optic or sight becomes unusable. However, because they are fairly small objects, it’s possible that they could become damaged if the rifle was dropped on a hard surface.

In order to test whether certain popular BUIS would still be serviceable after taking a hard hit, I attached three different types of BUIS – Troy Industries, Magpul Industries and Diamondhead USA – to an AR-15 rifle chambered in .300 AAC Blackout weighing 7 pounds and dropped the rifle upside down from a height of 5 feet onto a concrete surface.

Other portions of the rifle were protected from damage, and each set of BUIS took a solid hit from the drop. The ammunition used was Remington Premier Match .300 AAC Blackout 125 gr OTM. Each sighting device was installed according to the manufacturer’s instructions, then points of impact was established from a stable shooting position at 25 and 200 yards. After the drop, the rifle was fired again, and any change in point of impact noted.

The first BUIS dropped was the Diamondhead. At first, damage appeared cosmetic only; however, the apertures could no longer be rotated, windage could not be adjusted, and there was a definite cant to the BUIS. Point of impact shifted approximately 16 MOA. We contacted Diamondhead with this result. They replied that a newer version was available which was more durable. We offered to test the new model but production issues meant they could not ship one to us.

 Next came the Troy sight. Cosmetic damage was apparent, but the sight could still be operated normally. Point of impact shift was approximately 3 MOA.

The last set of BUIS was the Magpul MBUS. Damage was purely cosmetic and the sight remained fully functional. Point of impact shift was less than 1 MOA. Unlike the other sighting devices, a second drop was performed. Results did not change, and the sight remained functional.

Back up iron sights from Diamondhead, Magpul and Troy after being dropped on concrete.

Prior to this test, I didn’t think much of the MBUS; I now have a different opinion. In any case, it’s fair to say that I found the results of this experiment educational and informative.

[ Andrew Tuohy served with the US Navy as a Hospital Corpsman HM2 (FMF). Today, when not blogging, he is the “Resident Firearms Guru” at ]

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Matthew Cox
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  • oscar

    And this is why Magpul Original Equipment is the preferred aftermarket accessory.

  • SleepyDave

    Man, Magpul has really got this cheap-but-reasonably-durable thing DOWN, don’t they?

  • I wish they would of checked a few from Yankee Hill Machine. I have two of theirs. First came with upper I ordered it was the YHM-9680. It seemed to be a bit on the minimalist side, not particularly strong and it had no elevation adjustment. So I picked up the YHM-643K very robust, though it doesn’t fold down, it does have elevation. Didn’t care for the allen wrench screws for lock down and replaced with hex screw. I think if I’m going to iron I must of broken the Eotech or the scope, so it is more a matter of putting on and leaving on. So elevation was a factor then. They do make two more like the review models. The first is the YHM-5010 which springs up and can be had with either small, large, or duel peep sight. The next is the YHM-5040’s the back sight is basically the same as YHM-5010 just with the Todd Jarrett Strike Force logo and comes with a front sight.

  • gunslinger6

    I have already ordered the Magpul waiting on it to be delivered. I was excited to receive it already but this article just confirmed what I already new that Magpul makes great stuff!

    • xcalbr

      for what you get for the cost, it is my opinion that the Magpul MBUS is the overall best choice for backup iron sights.

      Their construction out of polymer brings concern to gas piston AR15 users (and DI as well in smaller numbers), who fear they will melt due to gas block temperatures, though I have never had any problems on both of my DI or gas piston carbines.

      • Jim

        Don’t know if I understood you right but the MBUS is not designed for gas block installation.

        • xcalbr

          i was pertaining to mounting on the rail directly above the gas block on a rail, which doesn’t cause any issues. as for mounting it on a railed gas block…its something i wouldnt do if you use automatic fire mode or put a lot of rounds down range in a short period of time.

          • Jim

            I wonder what you could get away with before they would melt


    This is a case where the elasticity of polymer proves it to be superior to thin metal- the polymer sight can absorb and dissipate the impact while the others bend or break.

  • NMate

    I’d have liked to have seen KAC’s BUIS tested. I don’t know about their durability, because I’ve never tested them. As far as replicating the A2 iron sights, they’re the best folding sight I’ve tried (speaking of the full size and micro folding, 2-600m rear sights). I’d guess they’re fairly tough, they’re the only BUIS the military is regularly seen using. I’d like that confirmed for me, however.

    Speaking of the sights tested, I’d never thought much of the Magpul sights either. Apparently they’re pretty good.

  • Ryan

    I have the magpuls and i gotta say i love mine. Good product

  • straps

    Follow Magpul’s MBUS installation instructions TO THE LETTER and those sights will serve you well.

  • EGS

    i had a Gen1 rear MBUS break on a 3 foot drop from my bench when i was working on the upper, i hadn’t secured the upper properly and turned to grab a tool and the upper fell. in any case, the MBUS fell on one of the protective tabs broke at the adjustment screw, but did not break off. however, the sight was a little misaligned.

  • Pete Sheppard

    The Magpul in the above photo simply looks more rugged as well; the others look like they are just waiting to break off…

  • Jim

    I just put these on a DPMS. So far so good. Thinks it’s just a matter of how they land when they hit! For the money I think there a good option.

  • Jim

    If they do break easy to replace!!!

  • Jim

    Ran into a problem with the rear. These are fairly long and it interfered with the flip up lens cover on red dot scope I had. The MBUS had to be almost on top of the charging handle, just about hanging off. Be aware if you have a fairly long and low scope.

  • Jim

    I like the MBUS enough to get a different sight

  • Lance

    Im for Magpul alot less bulky and alot lighter and cheaper than Troy’s sight.

  • Joe Schmoe

    I used an A.R.M.S. #40 BUIS while in the army and it served me flawlessly for years under the harshest conditions (including drops).

  • xcalbr

    makes me feel better for using magpul’s MBUS on all of my builds. For the money, they are a hard set of iron sights to beat.

  • Were the sights open or closed during the impact?

    The pictured MBUS appears to be a Gen 2, is this correct?

    Thanks for doing this test, it was very informative. I would be curious about the results of a similar test on ‘fixed’-style BUIS like the DD A1.5 and the LMT Rear BUIS.

  • Maxx Ordnance

    With respect, if they break at the range, no big deal. If they break in a gunfight (after your optics are tango uniform) it could ruin your whole day.

  • Uncle Chewy

    I hear the French military are incredibly interested in any test involving the dropping of weapons to the ground.

    • fish

      hahahah that is a good one!! hahahahahah that is purely funny, and puts this drop test in a category of why?

  • Jim

    While at a fast pace!

  • I own a set of Troy Di-Optic Micro Battle Sights (w/ Tritium). They are fine sights, but nothing to brag about. I own SEVERAL of the Magpul MBUS sights, in multiple colors, on multiple different calibers (5.56, 300Blk and .308). My mind was made up on the difference a LONG time ago. If you want tritium, grab a Trijicon front post like I did. Looks good and works great. Call me a Koolaid drinker, I’m set with Magpuls from now on.

  • 3 of 4

    Interesting that the ARMS sight was not tested. With it’s spring loaded design, it would appear to very damage resistant.

    But ARMS is very politically incorrect, what with their defense of their trademarks against LaRue’s infringement.

  • billy

    How does the standard A2/A3 Carry handle fair in these same tests? Would be interesting to see.

    • Adam H. “Thanks for doing this test, it was very informative. I would be curious about the results of a similar test on ‘fixed’-style BUIS like the DD A1.5 and the LMT Rear BUIS.” and billy’s “How does the standard A2/A3 Carry handle fair in these same tests?”

      Would like my YHM-643K included. It seems a little more solid in that it clamps at two points.

  • It looks like the ‘release lever’ portion of the ARMS BUIS would be exposed and prone to breaking off while the sight is in the deployed position.

    Also, the numbers ‘3’ and ‘4’ have been previously trademarked and you are hereby ordered to cease using them in social media communications. No, wait. That’s silly. Just like the ARMS lawsuit.

  • From Andrew’s Blog (
    One thing I did not mention in the post which was sent to KitUp (due to word count limitations) was that after dropping the MBUS twice, I picked the rifle up, held it over my head like the maul I used to split seasons’ worth of firewood while growing up in Alaska, and swung it down on a concrete shooting table, with the MBUS taking all of the impact. It did not break or shift POI by anything more than 1MOA.

    My opinion of the MBUS went from “cool airsoft gear bro” to “wow.”

    Under that kind of abuse, it’s hard to imagine the long, thin aluminum carry handle not bending.

  • Jim

    Have seen carry handles destroyed just from gravity off the top of gun trucks.

  • Jim

    Hope your weapon survived the test and thank you!

  • Randy

    To the OP , a person asked…. We’re the sights folded or up in the use position for this impact test? Clarification? I have an idea the metal sights may fare better than polymer if in the up pos for test….

  • Adam

    the sights were in the up positions from what I can tell of the photos. which is when the locking metal sights would certainly be most vulnerable. I would have love to have seen this test done with the A.R.M.S. sights, which in my opinion are superior to the Magpul BUS Gen 2.

  • I have the ARMS polymer sights on two M4’s, & one of them broke the left ear off the rear sight when it slid sideways off the front of a chair & hit the carped floor. It was muzzle down (flash hider on floor), sights deployed in the “UP” position. It wouldn’t have fared as well as the Magpul MBUS sights in this drop test. Not even close.

    • Adam

      no kidding? that is a little concerning, They seem very rugged to me, but I do also have a nice set of Troy DOA brand new in the box incase anything ever does happen to my ARMS, but my main optic is an Aimpoint H1 Micro and doubt I’ll ever even need to deploy my ARMS. but now you got me thinking…. I am pretty sure the Navy did extensive testing on the ARMS, wish we could see their reports on them since they did choose them as a backup sight.

  • Shem Rock

    I have seen the U.S. Military are perfect for storing your ammunition and other valuables. These cans are Made in the U.S.A. and are designed to keep your items dry and clean.

  • I love Magpul, my main AR is outfitted in all MOE furniture.

  • JohnD

    Never liked the flip up,site issued with the M4. It would not stay down and caught on everything throwing off he sight. Had one on my M-16A4, same deal. If I had to go again, I’d buy a MAGPUL!