Unique AR15 jam. . .

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edwardware

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I'm working up load data for a couple powders in a sorta-wildcat cartridge (7.62x40WT) in an AR platform. With this in mind, it could be under- or over-gassed (excessively slow or fast powder).

As I've been working up, I've twice seen a jam that is completely unique in my experience. The mouth of a fired cartridge engages the inside of the charging handle nose, the head of the cartridge stays on (or re-engages) the bolt face, and the BCG hangs half-shut. Of course this can't be cleared from the charging handle; you need to pull the BCG back through the port.

So, what does this FtEject suggest to you? Something about gas supply, or the bolt perhaps? The bolt appears fine, ejector and extractor are good as far as I can tell. It's occurred with recipes that usually eject and lock back, and both with and without a magazine in the well.
IMG_20201103_182217698.jpg IMG_20201103_182251217.jpg

Edited for Spelling, thanks @jmr40
 
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Something likely not right with the ejector. It should be turning the case towards the window And keeping pressure on it to spit it out when the bolt retracts enough for the case mouth to clear the window. Something is turning it straight up, just gotta figure out what it is.
 
I don't know if it's possible. I don't have an AR in from of me.

Can an AR bolt be installed in the BCG rotated 180 degrees out of its proper position?
 
gpb said:
I don't know if it's possible. I don't have an AR in from of me.

Can an AR bolt be installed in the BCG rotated 180 degrees out of its proper position?
Click to expand...
No. The gas key is what aligns the bolt and forces it to be properly located at time
In install and to remain in proper location.
 
I have seen jambs like that, not really uncommon. Definitely check that you have the correct extractor and spring and that it is set up/working correctly.
 
And now a whole crop of various Failures to extract (and consequent double-feed). The Extractor feels ok, and yes it's pointed out the port, but I wonder if it's floating.

The cases it fails to extract have no rim damage at all. . .

jmr40 said:
Jam. . . jamb
Click to expand...
Speeling Maaterz. . .
 
Maybe, if the bolt is short stroking just the right amount, could the mouth of the case come out of the chamber but the bolt started to close before the mouth gets to the ejection port? Do similar loads lock the bolt back on an empty mag?
Otherwise, I'd have to agree on the ejector not putting enough force on the case head.
 
Is it a problem unique to your loaded ammo or is it happening with factory stuff as well? At least that way, you'd be able to determine if it's a gas/ammo problem or a gun issue.
 
I had a 300 blackout do that. The extractor was releasing the brass as soon as it cleared the extension. If the bolt came back fast enough it usually ejected, but if done slowly it would almost always drop the case before ejecting it. Longer .223 cases worked fine. Dunno if it's a related issue, as the WT is longer.
 
Judging by your shell deflector it looks as if the brass that is extracting and ejecting correctly are headed in the correct direction.

Your BCG looks dry, I run all my AR's wet, might help your scenario a bit.

If it were me I would be looking at the extractor and ejector which it appears you have already looked at; and in particular the ejector as it looks like it isn't forcing the case towards the ejection port.
 
If it were over gassed it would leave the case in the chamber marking up or tearing off the case rim, showing the extractor weak.
Under gassed and we’d just be talking that.

My guess is the case rims are a bit thin for the extractor to hold on to, or the extractor groove is shallow. The next round bumps the case up, since the extractor won’t hold it to the ejector to go out.
The bolt doesn’t pick up the next round because it gets the same one back and the case head blocks the next round.

But, that’s just a wild guess, since you said it was Wildcat.

What’s the “WT” stand for?

I’d love to have an adjustable gas Nemo or some such in Thirty Aught Six. But that’s proprietary, which I’ve found more expensive than wildcat.;)
 
Cemetery21 said:
Maybe, if the bolt is short stroking just the right amount. . .
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The first test for working up was a recipe's ability to reach bolt lock without overpressure, so it's not a shortstroke.

armedwalleye said:
Is it a problem unique to your loaded ammo or is it happening with factory stuff as well?
Click to expand...
There is no factory ammo. . . it's entirely off the reservation!

BreechFace said:
Judging by your shell deflector it looks as if the brass that is extracting and ejecting correctly are headed in the correct direction. . .
If it were me I would be looking at the extractor and ejector which it appears you have already looked at; and in particular the ejector as it looks like it isn't forcing the case towards the ejection port.
Click to expand...
Maybe I haven't looked enough. I wonder if a weak extractor spring might be just enough to turn the case loose before the mouth clears the extension. . .

Riomouse911 said:
I agree, the extractor is dropping the case before it should or the ejector isn’t sending the case out the port well enough to avoid the bolt returning home.
Click to expand...
I think this is where I'm headed.

Demi-human said:
What’s the “WT” stand for?
Click to expand...
7.62x40 Wilson Tactical. It's a cool name, a SAAMI drawing, and 0.035" case length shy of the Wilson .300 HAM'R. The brass is a simple form away from 5.56, but much longer than .300BO to waste less magazine length for 110-150gr bullets.

Thank you all, I appreciate your ideas! I think I'm going to chase an Extractor issue. . .

762x40WT-cartridge-case.jpg
 
LoonWulf said:
The extractor was releasing the brass as soon as it cleared the extension.
Click to expand...

That was going to be my suggestion. I had an M16 in the Army that would do that... the fired case would, in some cases, get jammed between the upper and the gas tube, completely jamming the weapon. Armorer changed the extractor and extractor spring... and all was fine.
 
edwardware said:
...I wonder if a weak extractor spring might be just enough to turn the case loose before the mouth clears the extension. . .I'm going to chase an Extractor issue. . .
Click to expand...
If the AR doesn't have a Colt or Sprinco extractor spring, it has a weak extractor spring. The extractor may also be out of spec.
 
The donuts cause more problems than they fix. Use the right spring to begin with. (see above.) They're not needed. They're the lazy Armorer's quick fix, instead of doing the job right. I also suspect that with that gun increased spring rate won't be necessary once it is repaired.
 
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