I’ve been shooting the AR/M16 platform a long time and am a Colt armorer, but this one was new to me.
I was running range drills for a group of shooters, one of which was using a fairly low mileage (under 2k rds.) Bushmaster M4’gery with a BM 20 rd. magazine (also low mileage) and firing factory Remington 55 gr. FMJ ammo.
About 10 rounds into this mag his BCG stopped approximately halfway forward. Examination revealed an empty case was now loaded in the magazine, with it’s mouth barely past the front of the mag.
I first suspected an empty had somehow been loaded into the magazine, but the case was hot. This brass was from the round he’d just fired.
The shooter continued using this magazine in his rotation and fired several hundred more rounds with no further stoppages
I’ve never seen this before and am stumped as to how this could’ve possibly occurred.
Anyone seen this before or able to offer opinions on how?
Honestly I think your first hypothesis was correct. Somehow an empty round was loaded into the gun. It is possible that the round headed up a bit from contact with the bolt, etc and this is why it is hot.
However it is possible that there was some strange, one in a trillion chance of something happening that would lead to the round not extracting but the bolt hitting it at an angle that would push it down into the mag. I don’t see how but I have seen stranger things happen in my life.
kewlz is spot on- spent case in the mag perfectly answers the question, ride foward until the neck strikes the receiver. the odds of an extracted case rattling its way back into the mag are astronomical
I agree that this seems to be an impossible occurrence, that’s why I’m fishing for some sort of explanation.
The shooter - who had just loaded these mags himself - was a former TAC team leader with quite a bit of experience with this firearm and an all around on the ball individual.
This occurred during a relatively short string of fire (the weapon wasn’t truly hot) and the empty case didn’t have time to heat up from contact with the bolt before he dropped the mag - the case was actually HOT. I was standing alongside him as this occurred and saw his bolt stop short, but allowed the shooter to discover the issue on his own in order to gauge how he dealt with it. He cleared the mag out quickly.