AR Tearing Rim Off Case

[HT4]

My suppressed AR SBR that has shot a few thousand flawless rounds decided to start tearing the rims off of factory loaded Remington .223 cases today. Pictures attached. I switched ammo and it stopped. FWIW, I built this AR. The barrel is noveske with a pre-pinned gas block. 10.5" w/ carbine length gas system. The gun runs a stupid heavy 9mm buffer with a weighted BCG and +p spring when the can is on. I've never used polymer or lacquer coated rounds in the gun. Any thoughts on the exact cause? Weak cases, Over pressure ammo? Seem unlikely with the UMC I was using, but always possible. Absurdly over gassed? Something else?

If this happened on day 1, I would be thinking about a pigtail gas tube, adjustable gas blocks, sending the barrel back, etc... but this is after a couple dozen range trips. Thus, I am leaning towards bad brass, but would like to hear other opinions.

 

[blodter]

Seems like your gas system needs to be adjusted whenever you're using a suppressor, or just use ammo loaded at a lower pressure. I've heard that JP has some great adjustable gas systems for a fair price, whilst maintaining a very high quality!

http://www.jprifles.com/1.4.6_gs.php

 

[BradMacc82]

Had one upper that'd rip the rims off on one specific type of ammo, even with the boards help, couldn't figure out why or get it to stop.

Stopped using that ammo, ran just fine with every other brand.

 

[clandestine]

Bad ammo. PMC and UMC sucks IMO. Especially in good barrels. Steel cased ammo is more predictable than that stuff IMO

Pigtails are worthless.

Adjustable Gas Blocks are not so great unless you want to fork out about $100 for the detent adjustable models, which are nice. Without a detent you can't repeat your settings with suppressor and ammo changes, with a click dteent you can.

 

[Evil Twin]

Seems Remington can't get anything right these days.

 

[Blaster229]

I find it an amazing coincidence that they were both torn right at the .223 part of the rim.

 

[traveller]

I find it an amazing coincidence that they were both torn right at the .223 part of the rim.

You may be on to something. If you look at the remainder of the headstamp it is off center and there is a wider margin to the edge of the case on the 'R' and 'P' marks. I would like to see a picture of an unspent round to see whether the .223 runs into the edge causing a weak-point.

 

[HT4]

Had one upper that'd rip the rims off on one specific type of ammo, even with the boards help, couldn't figure out why or get it to stop.

Stopped using that ammo, ran just fine with every other brand.

What brand?

Seems like your gas system needs to be adjusted whenever you're using a suppressor, or just use ammo loaded at a lower pressure. I've heard that JP has some great adjustable gas systems for a fair price, whilst maintaining a very high quality!

http://www.jprifles.com/1.4.6_gs.php

The only change I make when putting the can on is to add an extra 4oz weight to the BCG. Seems to help -- the gun is a soft shooter. Unless I went with something like a switchblock, I can't see myself taking out a hex wrench every time I put the can on.

Bad ammo. PMC and UMC sucks IMO. Especially in good barrels. Steel cased ammo is more predictable than that stuff IMO

Pigtails are worthless.

Adjustable Gas Blocks are not so great unless you want to fork out about $100 for the detent adjustable models, which are nice. Without a detent you can't repeat your settings with suppressor and ammo changes, with a click dteent you can.

Thanks... coincidentally, this particular range trip, all I had with me was UMC and PMC. Both about 5+ years old. What is it about "good barrels" that make them particularly troublesome with these brands?

I find it an amazing coincidence that they were both torn right at the .223 part of the rim.

Interesting observations... might be something to it.

 

[clandestine]

Noveske Chambers will eat crap ammo generally but IMO, UMC is generally bad ammo. I have never gone into figuring out why, I just avoid it now. PMC seems to be problematic in some AR's. I think it may be the powder they use in certain loads but again, I haven't done a thorough investigation, I just don't use the stuff.

Some barrels will have shorter throats causing a pressure spike, this can cause extraction issues. Those cases don't look like they stuck though on the outer walls. If the throat is full of nasty buildup your accuracy can suffer bit I haven't seen copper buildup cause pressure issues.

 

[BradMacc82]

Silver Bear was always my nemesis with 1 particular upper.

Will not speak it's name, may bring back bad memories for Chad.

 

[clandestine]

Damn babnannas

 

[BradMacc82]

Damn babnannas

Watch your mouth mister....

Or I'll stop making the clips for your trashcan AK.

 

[clandestine]

LULZ

 

[iH8DemLibz]

I will add my .025

Maybe your good barrel has an extremely tight, but still to spec chamber.

Maybe the cases have to compress some in chamber, but they still chamber.

Maybe they are just a tad stuck in the chamber and it takes more force to extract them.

Also, if you look at the right hand picture, the top of 223 stamp is very close to the primer.

I'm thinking it's just a coincidence.

 

[HT4]

Noveske Chambers will eat crap ammo generally but IMO, UMC is generally bad ammo. I have never gone into figuring out why, I just avoid it now. PMC seems to be problematic in some AR's. I think it may be the powder they use in certain loads but again, I haven't done a thorough investigation, I just don't use the stuff.

Some barrels will have shorter throats causing a pressure spike, this can cause extraction issues. Those cases don't look like they stuck though on the outer walls. If the throat is full of nasty buildup your accuracy can suffer bit I haven't seen copper buildup cause pressure issues.

I will add my .025

Maybe your good barrel has an extremely tight, but still to spec chamber.

Maybe the cases have to compress some in chamber, but they still chamber.

Maybe they are just a tad stuck in the chamber and it takes more force to extract them.

Also, if you look at the right hand picture, the top of 223 stamp is very close to the primer.

I'm thinking it's just a coincidence.

The broken cases above were hard to remove from the chamber... I could not pull them out from the breach. Is that normal?

If I did not have an AK with me, the gun would have been down for the session... As much as I hate to use steel on steel, I had to use the AK's cleaning rod to clear the cases.

It did occur to me that MK would be chuckling in heaven to see his creation used to fix an AR. In any case, a cleaning rod is now part of my range bag (rather than the bore snakes I had before).

 

[Silverlode]

PMC seems to be problematic in some AR's. .

The PMC Bronze .223 only or is the XTac crap too?

 

[BradMacc82]

Xtac is marginally better, from my experiences.


I'll have to run a batch of Remington brass thru my AR and see if the same issue arises.

 

[iH8DemLibz]

I would clean the snot out of that chamber and see if it happens again with the same ammo.

If the extractor would not remove it, then it is normal that your finger pressure would not remove it either.

Again, this is just my opinion, but there is some crap ammo out there. Just like everything else being sold in the market place.

I had a Brown Box of 193 Federal 556 and the brass was not even cleaned. One ENTIRE case from top to bottom was covered in permanent black marker. The other cases looked like they were range pick-up brass that was sitting outside for a while. Anything to save money these days and I won't be buying anymore of it.

I've put thousands of rounds of PMC through mine with no problems. Actually, no problems with any ammo.

I will be spat upon by some for saying this. Put a bit of green cleaning pad on a bore brush and scrub the chamber using a cleaning rod chucked up in a drill. Keep it wet with bore cleaner while working. Run some clean patches through it and your done. Don't let anyone tell you that it will make your chamber too big by removing metal.

If it keeps happening, take it to a "real" gunsmith and have it head spaced. Even "good" barrels are being cracked out at blinding speeds with little to no Q.C. inspection.

 

[clandestine]

Use Wipe Out, not abrasives in that barrel.

 

[coopermania]

I would clean the snot out of that chamber and see if it happens again with the same ammo.

If the extractor would not remove it, then it is normal that your finger pressure would not remove it either.

Again, this is just my opinion, but there is some crap ammo out there. Just like everything else being sold in the market place.

I had a Brown Box of 193 Federal 556 and the brass was not even cleaned. One ENTIRE case from top to bottom was covered in permanent black marker. The other cases looked like they were range pick-up brass that was sitting outside for a while. Anything to save money these days and I won't be buying anymore of it.

I've put thousands of rounds of PMC through mine with no problems. Actually, no problems with any ammo.

I will be spat upon by some for saying this. Put a bit of green cleaning pad on a bore brush and scrub the chamber using a cleaning rod chucked up in a drill. Keep it wet with bore cleaner while working. Run some clean patches through it and your done. Don't let anyone tell you that it will make your chamber too big by removing metal.

If it keeps happening, take it to a "real" gunsmith and have it head spaced. Even "good" barrels are being cracked out at blinding speeds with little to no Q.C. inspection.

The thought of spinning a abrasive in a chamber with a drill and its not going to make the hole bigger when metal is removed is silly.
With your thinking you can drill a 1/4" hole with a 5/16" drill bit.