I dont want to send my upper to rock river if i dont have to, but about 1 out of every 20 rounds will fail to extract, and become stuck in the chamber. When i tap the fired brass out from the muzzle end, there is a piece of the rim ripped off from the extractor. I am taking it to my gunsmith tomorrow to check the headspace, he said he had seen similar problems from 6.5 grendel barrels that needed the gas ports opened up, to me it seems like the chamber is to tight, causing excessive pressure required to remove the brass, but i could possibly understand the port solution if opening the port slows down the timing allowing the brass to contract slightly and come out easier. The gun is a rock river lar8 with a vltor stock kit, and a daniel defense handgaurd. It has roughly 500 to 700 rounds total through it, and the problems seem to only happen with military ammo, m80 ball, first w/ some old surplus i picked up at a show, and now with some new stuff. It has never happened with winchester 308 hunting stuff, even when reloaded. I will try to get pics up in a day or two. Any help is appreciated, thanks and happy veterans day to all who have and are serving.
trying to post pic…
pic attached
I’m no expert but I actually stayed at a holiday inn express last night,
I suspect you have a 223 chamber.
Sorry my mistake it appears you have a308 chamber instead of a 7.62 NATO chamber
Opening the gas port will actually cause more gas to flow and won’t solve your problem as far as I know. I suspect an issue with the chamber.
This.
Also might want to check your extractor and springs, as well as your action spring.
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It sounds way over-gassed.
probably this
I dont think i explained it clearly to my gunsmith when he thought it was an under gas issue. I know stamped numbers dont mean anything, but the barrel is marked 7.62x51, and the manual says you can shoot anything under 2700fps. The extractor is working fine and i do remove it to clean behind it after each range session. If you look close enough at the pic, you can see that part of the rim is missing from the extractor doing its job. Thanks for the replies, keep them coming.
As others have stated above, it’s probably a chamber issue.
Heavier buffer or spring to slow the timing allowing pressure to drop?
Not a pro, just throwing an idea:)
I thought that too, but it seems like a band aid for the real problem, i’ll keep you posted.
it really sounds like a bad chamber, way too tight, the extractor is working well because of the piece taken off the case, if it were me I would find a go, no go gauge and check the chamber, I would say find a reamer but they r kind of expensive if you dont have multiple projects that a reamer is needed. You could try and polish the chamber, that might help.
If you can get ahold of a gauge, id check it, and if out of spec, send it back. You dont want to pay for something they messed up. If you buy a new car and it keeps stalling out - do you fix it yourself or take it back to the dealership? 
Gool Luck and hope it works out for you.
if it were me I would send it back before pay for a reamer if the chamber is out of spec, that would be my advice.
I agree send it back, hopefully they will remedy the issue.
I’ve seen this before on the RRA 308s that come through the shop.
Check your chamber dimensions. It sounds like it’s too tight and when it warms up it seizes.
If it’s a stainless barrel or isn’t chrome lined reaming the chamber won’t be too cost prohibitive. If it is chromed… send it back and demand a properly reamed one. (Reaming chromed chambers sucks balls)
Definitely slap the power drill out of the hands of anyone who says it is under-gassed.
Most likely, a tight chamber, or a short throat/leade. First step, send it back, with a fired case.
If it comes back and still does this, then it is time for delicate measuring as to chamber size and throat length.
The barrel markings, in many instances, do not mean anything.
My Le901 did the same thing with M80 ball this week. It was magtech and had the green sealant around the primer. Is that what Ammo you are shooting?