So I get a call from this guy I know, generally a real calm sort, and real safety-minded when it comes to guns or anything else. He's a little worked up. Says he just put a round in the dirt about 4" in front of his big toe. I say "Well heck, at least your muzzle was off your personal assets. Finger off bang switch Amigo..." He says "NO, I didn't have my finger in the trigger guard. You need to look at this thing! All I did was rack a round up and BOOM."

Well yes, by golly I DO need to see that. The halves get separated and here's what we find-

Closer...

and finally...

The castle nut could be turned easily with your fingers and the buffer tube was backed out clear of the detent port. When he racked the round up, the detent finally popped out and the buffer over-rode the hammer & knocked it out of engagement with the sear. If you look closely at the middle pic you can see where the hammer scored the face of the buffer when the rifle fired. The detent ended up in front of the hammer, captured when it returned forward again.

This is reportedly a relatively new DPMS A-15 with less than 100 rounds through it, used by two brothers at different times. I don't know whether the castle nut just wasn't tightened properly at the factory or if somebody had their fingers in it. I won't speculate. I do believe this is an unusual, mechanically caused accidental discharge. Thought I'd share it for the informational value.

Oh, and the lower wasn't damaged at all. The rifle was reassembled properly and passed all function and safety checks. Test fire this weekend.

Right now, I've got a double-back to day shift. Check in over the next couple of days.

New one on me, for sure. I'm wondering if it turned a full turn out, like maybe got bumped halfway around and just spun out instead of in by hand. I've seen people stake the back plate into the castle nut before and thought it was a but of overkill. It maybe not! I'm kind of surprised that. nothing was whacked hard enough to damage it. Its good the buffer self aligned back into the tube as the bolt came rearward.

part rather than just depositing it under the hammer. Why, because the nut removed the nut to install a single-point sling loop and didn't properly adjust the attachment. Two rounds and the buffer and spring did what this did. A cautionary tale!

--
Sincerely,

Hobie

that A) nobody got ventilated and, B) nothing got broke. Apparently these boys' Mama prayed for them about as hard as mine did, for me.

buffer and spring spanned the joint between upper and lower at the rear of the receiver and were putting pressure on the parts such that removing the forward pin was a pain. The buffer retainer was crushed and had to be replaced.

--
Sincerely,

Hobie

After the nut is torqued to 25-30 ft poundees, you stake the receiver plate into the castle nut.

Then THIS doesn't happen at embarrassing moments.

the buffer. How it got in there I still don't know, I mean I know but I didn't think it possible. It wasn't due to a loose castle nut but a standard A1/2 extention and a lower with hogged out (bent out foward) detent hole.

I always joke about my castle nuts not being staked, but then half my gas keys aren't staked either. ;)