The first time out with my Bushmaster M4A3 16" carbine had major Bolt Carrier Assembly failure. Gun was brand new from Bushmaster no modifications other than a tripod and a carry handle scope had been added to the gun. Ammo was 55 grain FMJ Sellier & Bellot. Shot about 750 rounds thru the gun usually one 30 rd mag at a time but did fire a couple back to back a few times. Gun was working great no issues at all. The mag was a new one with the green follower.
The bottom of the Mag was blown out along with all the inards of the mag and about 18 rounds of ammo. The dust cover was blown off the gun, the mag release and bolt catch were broken. After Bushmaster recieved and tore the gun down they said the upper, barrel, the mag release, and bolt catch would need to be replaced at the tune of a little more than $300 since it was an Ammo problem.  I have used them in the military, but this is the first AR-15 I've owned.
My question is does this sound like an ammo issue?

Here is the response from BM

  No indication of a squib round was found in the bore of the barrel.
>
>      Damage occurred to the rifle due to cartridge case head failure by an
>over pressure round that forced the bolt to unlock while there was still
>pressure in the bore. The unsupported case head failed allowing hot gasses
>under pressure to be blown back into the rifle causing the damage to the
>parts.

I suspect Bushmaster knows what their talking about, IF as you state "they" have examined the remains of the rifle and told you so.

If I had to quess I'd say you were a victim of set-back or a squib round.

Mike

Quoted: I suspect Bushmaster knows what their talking about, IF as you state "they" have examined the remains of the rifle and told you so. If I had to guess I'd say you were a victim of set-back or a squib round. Mike

Of course Bushmaster is going to blame the ammo. Could have told you that without asking them.

Anything else, and they are liable.

Ammo?  pffft. What is a round going to do to blow up a bolt, magazine, dust cover, mag release, and bolt catch? (squib notwithstanding)

are other guns KB-ing with the Sellier & Bellot?

I would have included a mutual source to see /evaluate it. But then again, no one was hurt. And we are talking $300.......


although I think BM should pick it up.

There have been numerous issues with S&B rifle ammo.  Glad everyone is OK.

Quoted: On a side note, this isn't the first time i read someone experienced a kaboom using S&B ammo. If i were you, i'd post this thread ( or a similar one ) in AR discussion as a warning to other arfcomers. Glad you're ok. HUNTER.

If your going to do this suggest you provide abit more details as to the specific version of S&B ammunition you were shooting.

Old steel cased, (came in cardboard boxes of 140 rnds) new production brass cased, (in 20 rnd packaging), M855, green tipped....etc...., it'll help others.

Mike

Just curious, but out of those 750 rounds you fired, did you stop and clean/lube at all?

I'm sure an AR-15 should be able to hold up to that on its first outing, I just don't do that to mine.  Once I put 500 through at the range, I do a quick clean/lube.  But I'm kinda anal about making sure its clean and good to go.

As far as the ammo it was a new case of  production brass that came in 20 rd boxes. It was not the green tip, it was M-193/No. 2903 with 4.4 Boxer primer. It was in great shape with no rounds looking damaged or anything like that.  I was also under the impression that S+B  is a higher quality ammo.

As far as cleaning no I did not clean or lube while we were shooting. I inspected the carrier after every 5 mags or so and it did not look overly dirty and none of the parts looked any diffrent then they did before we started,except you could tell they had been in a gun that was fired. Also the gun was working great with no feed or ejection issues. I am sure there are guys who would not shoot 750 rounds in one day but I am sure a lot of guys do also. I don't get to go out as much as I would like so when I do it turns into a day event with mutiple people and weapons. I have friends with Bushmaster guns that have gone thru a 1,000  rounds a day when we go so I was not that worried.  

Go over to the ammunition forum and look for the thread on S&B ammo. It's been a while since I read it but I remember that it did mention numerous high pressure events with this brand and many people recommended against it. That forum has lots of info if some of yall have'nt been to it.
good luck with your gun.
leroy

I have fired exactly ONE round of S&B from my carbine...notice I didn't say extract and eject.

I ruined a cleaning rod bashing the steel case from the chamber.

S&B sucks hard. Bushy called it right, the ammo is to blame.

Quoted: I have fired exactly ONE round of S&B from my carbine...notice I didn't say extract and eject. I ruined a cleaning rod bashing the steel case from the chamber. S&B sucks hard. Bushy called it right, the ammo is to blame.

i agree def ammo problem there, stick with american made