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9/17/2020 5:59:48 PM
Posted: 6/24/2017 2:22:28 PM EDT
[Last Edit: 6/25/2017 9:04:28 AM EDT by ViktorVaughn]
As an anecdote or background, I have shot 10,119 rounds through various combinations of 7 lowers, 10 uppers (spanning 3 calibers), and 8 silencers and today was my first failure that resulted in "stoppage". I have had a few failures to lock the bolt back with old straight 20rd p-mags on my 300blk but that's it. So I have had very good fortune with this platform using good mags and good ammo (and good parts). But this failure is interesting and I can't quite figure it out.

The rifle in question is a 10.3" Colt barrel (w/ C7 type upper) using a Specwar 556k shooting PMC X-Tac 55gr from a 30rd P-Mag.

Illustrated here:


-Loaded a mag on a closed bolt
-Chambered a round via charging handle
-Fired the first round fine, hit where it should
-Went to pull the trigger again and no bang (can't recall if the trigger had reset or not)
-I assumed it was a failure to feed and charged the rifle again, seeing nothing in the chamber, but the bolt didn't go all the way into battery once I released the handle.
-Pulled the mag and tried to charge again but the bolt was stuck
-Mortared the rifle on the table using minimal force and out popped an unfired round that had a dent on the body extending to the shoulder
-Pulled the bolt and handle and inspected the chamber, bore and silencer. Nothing unusual.
-Rifle functioned fine after that

What I think happened was the first round extracted and ejected fine. But the second round never got fed. Nothing in the chamber. I charged the rifle again, it picked up the second round but only fed 90% of the way and got hung up causing the bolt not to go into battery.

Maybe the mag was not fully seated being that it was loaded to 30 and inserted on a closed bolt, and that caused the round to not feed and then mis-feed?

Either way I thought it was an interesting failure and one that caught me off guard. Trying to learn from it and figured I'd share.
Link Posted: 6/24/2017 2:55:39 PM EDT
I wouldn't worry about it unless it does it again.
Link Posted: 6/24/2017 4:02:54 PM EDT
Possible the mag wasn't fully seated. Was it a gen 2 or gen 3 pmag? I would think a gen 3 would be dropped after a round was fired if not seated. The gen 2s area little more snug in the mag well tho.

When you said the bolt was stuck I was thinking possibly a blown primer, but sounds like that wasn't the issue since you didn't find one
Link Posted: 6/24/2017 4:24:59 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By MILSPEC556:
Possible the mag wasn't fully seated. Was it a gen 2 or gen 3 pmag? I would think a gen 3 would be dropped after a round was fired if not seated. The gen 2s area little more snug in the mag well tho.

When you said the bolt was stuck I was thinking possibly a blown primer, but sounds like that wasn't the issue since you didn't find one
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Yeah blown primer was my suspicion at first. I've heard those can be a bitch.

I think the bolt didn't want to let go of the round and the round was so out of shape it didn't want to come out of the chamber. But a light mortaring freed it all up.

Not sure which generation of p-mag. Bought all my thirty rounders like 5+ years ago so whatever that would be.
Link Posted: 6/24/2017 4:35:55 PM EDT
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By ViktorVaughn:
Yeah blown primer was my suspicion at first. I've heard those can be a bitch.

I think the bolt didn't want to let go of the round and the round was so out of shape it didn't want to come out of the chamber. But a light mortaring freed it all up.

Not sure which generation of p-mag. Bought all my thirty rounders like 5+ years ago so whatever that would be.
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Discussion ForumsJump to Quoted PostQuote History
Originally Posted By ViktorVaughn:
Originally Posted By MILSPEC556:
Possible the mag wasn't fully seated. Was it a gen 2 or gen 3 pmag? I would think a gen 3 would be dropped after a round was fired if not seated. The gen 2s area little more snug in the mag well tho.

When you said the bolt was stuck I was thinking possibly a blown primer, but sounds like that wasn't the issue since you didn't find one
Yeah blown primer was my suspicion at first. I've heard those can be a bitch.

I think the bolt didn't want to let go of the round and the round was so out of shape it didn't want to come out of the chamber. But a light mortaring freed it all up.

Not sure which generation of p-mag. Bought all my thirty rounders like 5+ years ago so whatever that would be.
Probably gen 2s then. They're definitely tighter in the mag well, so mag not fully seated does sound like a good possibilty
Link Posted: 6/24/2017 10:25:18 PM EDT
Over 10.000 rounds and just 1 failure!   I love the reliability of the Stoner AR system.  
Link Posted: 6/25/2017 8:16:39 AM EDT
Originally Posted By ViktorVaughn:

-Loaded a mag with on a closed bolt

-Chambered a round via charging handle


but the bolt didn't go all the way into battery once I released the handle.
View Quote


yeah try not doing that
Link Posted: 6/25/2017 8:33:00 AM EDT

had a dent on the body extending to the shoulder
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Sounds like the bolt rode over top of the round so maybe a mag feed problem.
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