View Full Version : Firing from closed bolt vs. open bolt m16/m4

James H
December 22, 2010, 08:45 PM
For some reason I had this question pop into my head in a dream last night (I think about guns a lot). With a fully automatic capable M16/M4, do these rifles fire from the open bolt position when in fully automatic and then switch to closed bolt when in semi or 3-rd burst?

I've never even shot an AR15, so I have zero experience with the platform. Just wondering.

And by the way, I'm not looking for a run down on all the different models that are either 3-rd burst or fully automatic capable. That's easy enough to find on wikipedia. Just wondering about the fully automatic/bolt open question on the models that are full automatic capable.

December 22, 2010, 08:50 PM
closed bolt in all modes of operation.

James H
December 22, 2010, 08:52 PM
Thanks...that would make more mechanical sense.

B. Lahey
December 22, 2010, 09:40 PM
There was one model that fired from an open bolt, I think it was an experiment looking toward making a squad automatic weapon sort of deal out of the rifle. It never caught on; for what reason I do not know.

December 22, 2010, 10:03 PM
It was the LWRC M6A4, IAR. IIRC that particular rifle had 4 position selector. Safe, Semi, Safe, Auto.

From what I've heard from testers on site, Colt also had a rifle which would go open bolt after it reached a certain temperature.

Nonetheless, neither were selected and the USMC has selected the HK416, which from what I know, operates on closed bolt.

December 22, 2010, 10:16 PM

James H
December 22, 2010, 11:05 PM
Thanks for the video. The engineering must be ingenious. Especially a rifle that goes to open bolt once the barrel reaches a certain temp, like what was mentioned a couple of posts above.

December 22, 2010, 11:11 PM
Yeah, with the exception of some specialized LMGish variants that go to open bolt firing in full auto pretty much an AR derived weapon will fire from a closed bolt in all firing modes.

December 23, 2010, 02:14 AM
I think about guns a lotSo im not the only one?:p

any who, closed bolt on all firing modes.