Hey everyone. So I am having problems with my AR-10. It is a .308 and it is a DPMS LR 308 platform. It has a low profile non adjustable gas block. So, I have to use forward assist after every round or I get a light primer strike and it won't fire. When I chamber the first round by pulling the bolt back, it shoots fine but if the action is open after the last shot and I close the bolt by pushing the bolt release lever, it will not shoot unless I use forward assist. I have tried a stronger buffer spring but then it would be too stiff and it wouldn't grab a new round from the magazine. I cleaned my BCG thoroughly and have lube in all the right places. My next step is to replace the gas rings. Any other ideas?

sounds like the brass is not sized enough. are these your hand loads or factory loads?

I have used all factory ammo. Mostly military.

Clean your chamber - thoroughly.

Agree with GC. Start by using a chamber brush and clean thoroughly.

TC

You could also test the military ammo with a case gauge (never hurts if you got one).

TC

Who made the barrel?

Also make sure the gas tube and bcg are aligned properly and barrel nut gas tube are not touching. It would probably run without gas rings.

Might also check the barrel extension for burrs.

I would do a very thorough cleaning. If it only happened after firing a round, I would suggest checking your gas and recoil system as well. It should go into battery when using the bolt release. Clean it good, check the dimensions on the loaded ammo since it sounds like it may be mil surplus, also try a different magazine.

Thank you all for your replies. I have cleaned it thoroughly but I did not use a chamber brush. I will invest in one asap. The barrel is stamped, DPMS 7.62X51 with a 1-10 twist. I have tried different magazines with no success. I will mic my ammo and make sure that it's within tolerance. My buffer weight is not adjustable and I was thinking that I may need a new one so that I can adjust the weight. Thanks again for the advise and I will report back with, hopefully, positive progress.

Was it bought new or used. If bought new, it probabaly wouldn't hurt to manually cycle the BCG a few hundred times to speed up the break in period. Just adding some spitballs...

It was used but with a very low round count.

It may just need broke in really well. I had a 223 AR that took quite a few rounds to break in before it would seat a round every time. That and clean it really good.

have you tried more than one magazine?

you could easily be dragging on the feed lips or something similar. DPMS LR series rifles are known to be especially fond of magpul LR/SR series 308 mags. and we all know how fussy some metal mags can be. one wrong feed lip angle, or a little burr... and you got trouble.




as others have mentioned i would suggest hand cycling it to break it in after giving it a really thorough cleaning of the bcg, barrel, chamber, and barrel extension.

start by delubing the [beeep] out of it. take the BCG out and spray it with brake clean or gun scrubber. same goes for the upper itself. if you have an ultrasonic cleaner, disassemble the bcg and drop it in there first for 8-10 mins. then brake clean & scrub to get all the carbon out. when you reassemble you want that thing DRY DRY DRY. like painfully dry. you should cringe putting any rifle back together this dry type of dry.


then hand cycle it without any ammo several hundred times. pull the bolt and let it fly. wash, rinse, repeat. this dry lapping process will allow mating surfaces to smooth out on each other and run any burrs off that might be holding things up.

HTH and keep us in the loop on how things work out!