I threw this rifle together for my uncle. Its a DPMS Lower, Upper, and BCG. The barrel is a Black Hole Weaponry 1x11 mid length gas system. Hand guard is a Midwest Industries SS. He paid for all the parts and I just threw it together for him. I had to get a different barrel nut for the handguard they sent me because the one that came wouldnt line up with the gas port in the upper. So new nut came in i put the barrel in and put the hand-guard on and assembled the rest of the rifle. I have it back to him and told him to take it to a gunsmith and have the Head-space checked before firing. He calls me up the other day says its bad and jams up etc.

He hands me the rifle and two fired cases. I asked if the gunsmith used gauges before firing...he said no. Just tossed in 2 rounds and fired. Some gunsmith. I took one of the fired shells and put it in the chamber and dropped the bolt. Went to eject it with the charging handle and it took quite some force. Had to put the stock against my leg and pull back on the handle before it would eject. And i noticed that there are lines showing up on the fired cases. And i noticed that my gas tube isn't into the upper receiver very far. Wonder if someone out there knows how far it should be into the upper.


So to all those who know a lot more about these rigs then I do which isn't hard to achieve...what the hell is going on here.

You don't want to try and force fired shells into a semi auto, they swell after firing. Gas tube looks ok.

yeah i know but thats all i had to work with. I dont own a .308 and I couldn't find any snap caps at the local sporting goods store. Shit box of rounds is nearly 20 bucks and this isnt even my rifle lol. Not to mention he didnt get a magazine so the rounds are hand fed into the chamber instead of out of the mag. Another thing is I see this upper doesn't have feed ramps machined into the receiver. Is that a big deal? i wouldn't think so being that the early rifles didnt have them and they functioned.

Clean the chamber and oil the bolt up. Get a magazine and have the head space checked. I doubt its a head space issue but be safe. How do the primers look on the spent brass? Does it extract hard or load hard with an unfired case? How do the bolt lugs look? Lot of variables here. What ammo was it?

AL

You might take it to a gunsmith with a bore scope to confirm, but it looks like the chamber wasn't cut properly in the neck.  I had the same issue with a pistol barrel from a well known maker.  I assume those lines on the neck are evenly spaced all the way around the neck and are not just a couple scratches from feeding past the lugs inside the barrel extension.  It's a little hard to tell from the pic.

Right! If those marks on the brass are from the rifling do not shoot that rifle! that is scary wrong!

The gas tube does look about 1/4 inch short. All the guns I have the gas tube ends about 1/2 way down into the cut out for the cam pin.

The marks on the shell are common on DPMS from what I've seen (well, thats two LR308s...).  They're from extraction and scraping against the lugs while under pressure from extractor.

My LR is prone to getting very sticky when dirty.

I answered from memory and was wrong, mines like yours-

What ammo are you using? Commercial ammo comes with lots of room to spare, reloads that work in one rifle may not work in another. DPMS barrels have the tightest chambers based on reloader complaints posted on the web. Your barrel was made by an outside company and should be sent back to them with the bolt for their inspection and replacement. I suspect the barrel extension, chamber or bolt are out of spec OR your shooting reloads that haven't been resized enough to fit this chamber.

.308 rifles need a minimum of 50 foot pound torque on the barrel nut, I set mine at 70 lbs.

I noticed the same marks on brass from my LR-65... no problems.