One in a million AR15 issue

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ny32182 said:
(Unfortunate) update:
I've shot some of this ammo through a couple other rifles unsuppressed with no issues.

Took the rifle in question out again today and tried out H1 and H2 buffer. With the H2 buffer unsuppressed, the ejection pattern changed to about 4 oclock (good, right?) Put the can on. First 15 or so rounds were looking good (remember 50% of primers were coming out with the regular carbine buffer).

Then with about 15 total rounds of the ammo left, a primer came out. Went to unload to make sure it was out of the action. Bolt was in battery with a live round in it, but wouldn't move.

Chose to fire the round in the chamber. Bolt made it back to the unlocked position, carrier about a half inch from fully closed. Pogoing, etc didn't result in any movement. Went home, mallet to the charging handle, nothing. Put a rod down into the bottom of the case and hammered it back just far enough to get the empty case out. That puts the carrier just far back enough to where I can't separate the upper and lower. :(

I have no leverage to get the carrier back forward. I'm 99% sure the primer is wedged between the carrier and the inside receiver wall. Probably galling a nice groove in the upper.

Extension is staked on, so would prefer not to take it off, but I can't think of any other way to get it apart right off hand.... any ideas? Its locked up tighter than a drum.
Click to expand...

Exactly the situation the forward assist is for. ;) Try a rubber or dead blow mallet on it.
 
ny32182 said:
Bolt made it back to the unlocked position, carrier about a half inch from fully closed. Pogoing, etc didn't result in any movement. Went home, mallet to the charging handle, nothing. Put a rod down into the bottom of the case and hammered it back just far enough to get the empty case out. That puts the carrier just far back enough to where I can't separate the upper and lower. :(

I have no leverage to get the carrier back forward. I'm 99% sure the primer is wedged between the carrier and the inside receiver wall. Probably galling a nice groove in the upper.
Click to expand...

Actually it sounds to me like that primer is in the cam pin hole, not allowing it to move all the way back to the top where it needs to be for the carrier to come rearward past that area. Receiver extension probably needs to come off at this point, then tap bolt forward with the upper inverted, hopefully it will fall out. The cam channel in the upper may have a gouge though
 
Well I popped the pins and the upper and lower separated by a small amount. I put a rod down the bore with an empty case for cushioning on the bolt face and started tapping the assembly rearward. Taking a good bit of force. the receivers are separated enough now that I got the carrier back to where the key made contact with the top rear of the lower and I don't think it is going to move any more. I don't have a vice block or anything that will likely let me get enough torque on the castle nut to get it off.

Probably going to drop this off and the gunsmith and I bet he's going to need a grinder to get it apart at this point. Hopefully the lower and BCG can be saved.
 
taliv said:
. . . in this latter case, key is to recognize it quickly, because some of the remedial action drills will crush the primer in there and make it nearly impossible to extract.
Click to expand...
So, if it's behind the cam pin in the cam, the BCG will remain slightly OOB, and the bolt not quite rotated home. Right?
 
pictures would help, but yeah, take it to a gunsmith
 
edwardware said:
So, if it's behind the cam pin in the cam, the BCG will remain slightly OOB, and the bolt not quite rotated home. Right?
Click to expand...
i believe if the primer falls in the cam pin hole behind the cam pin, the bolt will go forward but only rotate partially, so not locked, as you say, and the carrier won't go all the way forward. however, you should be able to pull the carrier back, to unlock the bolt as long as you don't beat it hard enough to wedge it in there.
if it falls forward of the cam pin, the cam pin will not be able to move under the gas key and clear the notch in the upper receiver, preventing you from unlocking the bolt and pulling the carrier backwards.
 
But anyway, new data gathered today:

-I chronoed the Radway Green ammo, just over 3k fps from the 16" which from what I understand is right inline with what you'd expect from NATO spec M855.
-With the H2 buffer and can on, number of ejected primers dropped from 50% to one in ~15.
-As before, no primers ejected without the can, and the brass ejection pattern went from ~2oclock to ~4oclock. with the H2 buffer instead of regular carbine buffer.
 
i believe if the primer falls in the cam pin hole behind the cam pin, the bolt will go forward but only rotate partially, so not locked, as you say, and the carrier won't go all the way forward. however, you should be able to pull the carrier back, to unlock the bolt as long as you don't beat it hard enough to wedge it in there.
if it falls forward of the cam pin, the cam pin will not be able to move under the gas key and clear the notch in the upper receiver, preventing you from unlocking the bolt and pulling the carrier backwards.
Click to expand...

I was checking every piece of brass and saw the one with the missing primer. Gun was all the way in battery, but any easy pull on the charging handle produced no movement. I fired the chambered round and the carrier retracted just enough to unlock the bolt. From there it was locked down hard.
 
ok, i'm confused. you have the carrier far enough back that the cam pin must be forward under the key. you can't pull it any farther back because the key won't go into the receiver extension.

is it relatively easy to push forward almost into battery?
 
i reread your post above and think i understand now what you did. you do understand that by hammering the bolt, instead of the carrier, it will cause the bolt attempt to rotate, which pushes the cam pin into the side of the receiver. you probably have a lovely gash along the inside of the receiver. you need to figure out how to get the bolt to move forward inside the carrier. then it should move forward and backward freely. however, it probably won't go into battery. if you do get the bolt to move forward, invert the gun and try to shake the primer out of the hole.
 
entropy said:
Exactly the situation the forward assist is for. ;) Try a rubber or dead blow mallet on it.
Click to expand...

Only if the bolt is forward enough for the forward assist to engage the groves of the carrier.

Try this: Get a cleaning rod section, about 8 inches long. Get it between the upper and lower to the bottom of the bolt carrier. It won't take much effort so pry the bolt carrier forward until the forward assist can be used to get the carrier out of the buttstock, freeing your rifle.
 
i know what I would do if it was my rifle and the upper receiver is already trash. But it sounds like a gunsmith has it so, it’ll get worked out.

Likely it is a primer in the cam slot, but like @taliv stated you need to figure out why it’s blowing primers with that ammo, whether it’s gun or ammo related.

keep us in the loop.
 
Dropped off at the gunsmith... he's going to take the upper apart from the front (remove the barrel), then take the buffer tube off, and will have clearance to hammer the carrier back through the front.

taliv said:
ok, i'm confused. you have the carrier far enough back that the cam pin must be forward under the key. you can't pull it any farther back because the key won't go into the receiver extension.

is it relatively easy to push forward almost into battery?
Click to expand...

No.. locked up solid as pictured. Aluminum shavings were starting to come out here and there. I definitely still think the primer is wedged between the carrier and upper receiver wall.

i reread your post above and think i understand now what you did. you do understand that by hammering the bolt, instead of the carrier, it will cause the bolt attempt to rotate, which pushes the cam pin into the side of the receiver. you probably have a lovely gash along the inside of the receiver. you need to figure out how to get the bolt to move forward inside the carrier. then it should move forward and backward freely. however, it probably won't go into battery. if you do get the bolt to move forward, invert the gun and try to shake the primer out of the hole.
Click to expand...

Good point about the cam pin possibly being the source of the damage... however, I still think it would take major resistance to carrier movement for that to be a possible source (which there is obviously)
But yes, there is going to be a big gouge in the inside of the upper; It would probably still be functional, but I'm going to have it replaced. Hopefully everything else is still fine.

Gunsmith is also going to check chamber dimensions. My money is still on chamber being fine and it being an ammo issue, but, I'm not a professional gunsmith. :) I'll post final results.

Then I guess it is off to test with different ammo, but if I see one more primer pop, I'll be tempted to chuck it in the closest lake instead.
 
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