Safe to shoot Mk 311 Mod 0 in Bushy?

General Firearms Reloading & Ammunition
1

While reading this thread about bolt failures:

https://www.m4carbine.net/showthread.php?t=3807

I saw one poster talk about higher pressure from the 5.56mm .mil frangible rounds (which I am assuming are the Mk 311, Mod 0 DODIC AA40) and it causing problems. I’ve been using it for years on the firing range and never really knew that it was pretty high in pressure. But never had a problem out of my issue weapon. So question is…

Is this safe to shoot in a commercial Bushmaster with a 5.56 chamber that I have no idea if the bolt was MPI or HPT? I also have a batch tested barrel which as I know might or might not have been tested (which is 1/9 if that makes a difference for worse).

I’ve shot it before out of the Bushy with no problems, hundred fifty rounds or so…but long term liability? I want to avoid a kaboom if possible and a hundred and fifty rounds could be “okay, keep going,” “you’ve been lucky” or “not yet sparky.”

I have 800 or so rounds left (of the Mk 311) so to decrease the amount of wear and tear and possible overpressure, should I just divide it up among my other two rifles (Adcor piston and DD mid length that are HPT/MPI) to get rid of it? Or is it safe to continue to shoot in the Bushy?

Sounds like an obvious answer, but wanting to know if this stuff is as high pressure as the thread above stated and safe to shoot in a lower grade AR.

Did a search on it and the only close thing I came up with was the above listed thread on bolt failures.

2

I think it will wear out your bolt prematurely, but I dont think you should worry about a KB. I would just keep shooting it, dont worry about it, & when something breaks, just fix it. What gas system do you have?

3

I laughed out loud when I read the title!

Yes its safe, bushmasters aren’t the best in terms of reliability, but awesome ammo won’t hurt it.

4

I would say its a NO-GO i would get rid of the ammo. hold on I will send you my address:) No like they said shoot it if it breaks fix it.

5

Sure but that’s like putting high octane in a Yugo. Just something about it doesn’t seem right:D

6

It’s a Bushmaster lol, I kinda expect it to get worn out sooner rather than later.

It’s a carbine length so figure it’s going to be a bit rougher on the system than a mid or rifle length.

Thanks to all for the replies.

7

You’ll be fine. The bolt is a weak point in the M16 FOW period with repeatable failure modes (sheared lugs, cracked @ cam pin hole). It’s not exclusive to any one manufacturer but the ones that use non C158 or equivalent just seem to break faster. Bolts should be inspected regularly and replaced periodically.