AR-15 owners: You'll love this one!

[thinksnow]

@Johnny L.A.

You should also carry it with the dust cover closed.

There’s your answer: if you have the bolt carrier group forward and the dust cover closed, then drop the rifle on it’s butt, check the dust cover.

If it is still closed, the bolt did not move/cycle the action.

If the dust cover snapped open, then there is a chance the action cycled and you should check the chamber for a round before closing the cover.

[Scruloose]

Tripler, I got a reply back to my e-mail to the armory GM. It was a slow day today, so I also called the Gunner’s Mate “A” school instructors at Yorktown, and spoke with a Chief and Senior Chief Gunner’s Mate. FWIW, the Chief was a prior Marine who was well familiar with rifle fighting techniques. They all basically said the same things: while they haven’t heard of this specifically, it’s certainly possible. I guess that’s about what I was expecting them to say.

First, from the local GM:

As for dropping the weapon and causing it to cycle? The bolt only needs
to retract about 2 inches (less than halfway) to re-cock. A complete cycle
is something different. Every weapon has a cycle of operation, the M16A2
will fire, unlock, extract, eject, cock, feed, chamber and lock. I have
never seen this happen just by dropping the weapon. The weapon may re-cock
(with the bolt forward) if it is dropped on the butt stock very easily.
The bolt will definitely go forward if it is locked to the rear and
dropped. This is why our standard method of carry is bolt forward with an
empty chamber and loaded magazine in the well. As to prevent and
accidental chambering of a round. Hope this helps and is not to confusing.

He had to throw that last sentence in there because I’m a Boatswain Mate. Anyway, the instructors in Yorktown said more or less the same thing. I think of note, is they all agreed that if dropping or hitting the butt caused a full bolt cycle as described above, then something is definitely wrong, and repair is in order. They say that more likely, the bolt may be moving just far enough back to re-cock the rifle. As thinksnow points out, this may be easily tested. IIRC, that dust cover opens up right at the onset of bolt movement. None of the guys I spoke with ruled out the possibility of the rifle re-cocking without bolt movement; they just didn’t know as it had never come up before.

I was tempted to ask them to start dropping M-16’s and recording bolt movement in the name of fighting ignorance, but most GMs I know don’t have that type of sense of humor. So I didn’t.

FTR, we use the M-16 A/2, or M-16 modified A/1 lowers with an A/2 upper.

[Tripler]

Scruloose and thinksnow, I thank you guys for the research and hints!

Your armorer’s explanation does make perfect sense, and I’m glad I asked about it. I’m going shooting with my Pop this weekend, and I’m debating whether or not to see if each of my particular rifles actually cycles fully and chambers a round. If either one of them do, I know that I’ll have problems. Other AR-15 owners, YMMV.

Otherwise, it just sounds inherent in the design that the bolt only retracts a minor distance.

Tripler
Thanks guys!