Gunsmithing AR10 not extracting or feeding

[OEFDom]

Hey guys,

So I recently upgraded my DPMS AR10 and replaced pretty much everything but the barrel. I put the barrel on at 30ft lbs.

Took to the range today and it failed to feed from magazine. I ended up getting the round into chamber but didn't fire it, try to extract and it was stuck using federal ammo, not handloads.

Went home, loaded up a dummy 308 handloads and started tinkering. My first thought was for some reason, the magazine. Tried two pmags with same result.

When I pull the charging handle it'll grab the bullet but it gets stuck half way in denting the round. And when it does seat the bullet it gets stuck and I have to slight tap the charging handle backwards with a small finishing hammer, no damage very careful.

This rifle was stock prior to my upgrades but none of my upgrades should have messed with that.

The inside of chamber is very sharp and jagged and my conclusion is either that I need to back the barrel off just a bit to give it more room to seat the bullet (already at 30 ft lb minimum or I need to use a file and get rid of those Ridgid inside grooves just a bit. Your thoughts?

 

[ShtrRdy]

Did you replace the Bolt? And Bolt Carrier?

 

[OEFDom]

No it's the same too. Stock bcg and charging handle

 

[nn8734]

What is meant when you say “inside the chamber is very sharp and jagged?” No chamber should have any sharp or jagged surfaces. I’m maybe misinterpreting your statement there?

30 lbs is bare min for barrel torque (45-55 lbs is spec for most barrel nuts) so backing off any further isnt recommended.

Did you use a reaction rod to retain the barrel when torquing the barrel nut?

What specific parts did you change?

 

[2aBaC̶a̶]

Barrel ?
Upper?
Bcg?

Check the bolt outside the upper to make sure a round functions correctly with extractor and ejector.

 

[Maxduty]

Betting the barrel is causing an issue with the locking lugs, not the rounds. That it didn't fire sounds like a headspace issue. The barrel isn't seated nor is is torqued enough. Take it apart and try again.

 

[nn8734]

Take it apart and try again.

@OEFDom - And once it’s apart and barrel separated from upper, drop either a few fresh factory rounds or properly sized cases into the barrel to see if they fall in and out of the chamber freely. If they get stuck you obviously found the problem.

If you have go-no go gauges, I’d also check for correct headspace. Just something I always do before installing a barrel.

Assuming nothing gets stuck in the chamber, follow 2aBaBc’s extractor / ejector check suggestion.

Assuming that test also passes, reassemble the upper using a reaction rod (if you aren’t already) torquing the nut to 45-55 lbs. like Maxduty said, 30lbs is too loose.

 

[OEFDom]

Betting the barrel is causing an issue with the locking lugs, not the rounds. That it didn't fire sounds like a headspace issue. The barrel isn't seated nor is is torqued enough. Take it apart and try again.

Appreciate everyone's info, after the hard feeding and subsequent extraction, I didn't try and fire the round. More concerned with the problem at hand.

 

[OEFDom]

Thanks guys,

I think I have it figured out and wasn't anything I thought it was. After reading more, thought it was headspace issue as well. Ended up being much simpler than that. The buffer tube was threaded one thread to much, causing the bcg to not retract fully backwards by about 1/16th of inch to catch the back of the round in the magazine. This caused it to catch the first groove in shell right after the primer and before the body of the case, bending it upwards.

Why it extracts correctly now is beyond me but it does. Loaded up a dummy round and fed through mag flawlessly and extracted fine.

Appreciate everyone's input.

Dom

 

[2aBaC̶a̶]

So you had the tube over the buffer detent? Interesting that it would cause a fail to feed and that the upper would even close.

How does that explain the hard extraction? Unless your clambering a dented case.

 

[OEFDom]

So you had the tube over the buffer detent? Interesting that it would cause a fail to feed and that the upper would even close.

How does that explain the hard extraction? Unless your clambering a dented case.

Well the tube had a groove cut out for the detent, so naturally I placed the cutout around the detent. Like it looked like it should be. Negative, needed backed off one thread outside of the cutout and chambered fine.

So when it would half load, it was slamming the bolt into the round causing h very large dents, perhaps that was it.

 

[OEFDom]

What is meant when you say “inside the chamber is very sharp and jagged?” No chamber should have any sharp or jagged surfaces. I’m maybe misinterpreting your statement there?

30 lbs is bare min for barrel torque (45-55 lbs is spec for most barrel nuts) so backing off any further isnt recommended.

Did you use a reaction rod to retain the barrel when torquing the barrel nut?

What specific parts did you change?

Appreciate the advice, didn't know milspec was 45 to 55. I'll retorqued to 50, meet right in middle with it.

 

[nn8734]

Appreciate the advice, didn't know milspec was 45 to 55. I'll retorqued to 50, meet right in middle with it.

You’re welcome, man. Let us know if you have any other questions and we will do our best to assist.