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 LuckyGunner.com. ]