So I recently just built my first lr-308 and i'm having some troubles with it feeding. My first problem I had was a failure to extract, I put a BCM extractor spring kit in my bolt and that seemed to have solved my extraction issue. Now my issue is, when I fire my brass gets lodged between the bolt face and ejection port on my upper, and its getting lodged sideways most of the time. I have a syrac adjustable gas block on a rifle length gas system and have adjusted the gas block as much as I can and it hasn't helped. I've also checked to make sure my gas block is lined up properly on the gas port as well, so I'm at a loss for what to do on the gas system. My BCG is just a factory DPMS lr 308 BCG, and my barrel is a Brownells barrel, I have checked my headspacing and it is well within spec. My buffer is a factory lr 308 rifle buffer, and buffer tube. If anyone has suggestions on how I might get things working please reply!

What load are you shooting for starters?

The type of malfunction you are describing is a stove pipe malf.  The other one is either a short stroke, too fast cyclic, or FTEject with case caught in the ejection port.

Does a sized piece of brass or new cartridge drop into the chamber, or do you have to push it in all the way by hand (without the BCG installed)?

Will the cartridge fall out of the chamber with gravity alone, after fully being chambered (w/o BCG)?

Does the DPMS bolt articulate cleanly in the Brownell's barre extension, or does it drag, grind, or rub against the extension teeth in any way?

Is the BCG well lubed?

What mags are you using?

What receiver set did you use?

So as far as my receivers go, they're both dpms factory receivers. I'm currently using magpul pmags, i haven't tried any other mags yet, i need to. My loads i've tried have been PMC bronze 147 gr. FMJ, hornady 165 sst factory ammo, federal blue box 150 sp, and some hotter hand loads with sierra game kings and berger vld huntings. The round will chamber without any resistance and fall out with gravity alone, also the bolt falls into the barrel extension with no contact. I typically run my guns with either otis dry lube, or just some rem oil. This particular rifle i've used both on with no change in results.

What does your fired brass look like?

Will the gun fire one round, and lock back on an empty magazine?  That is usually the first live fire function test to conduct on a new gas operated rifle.

Are your PMAGs Gen I or Gen II?

Get some thick lubrication with good viscosity on that BCG either way. I use Slip2000 on my AR10 (my 5th AR10).  Only malfs I have had are from a closed ejection port start condition.  I need to put a stronger spring in the port door to fix that I suspect.

I have had to replace a lot of ejector and ejector springs lately, on brand new guns.

Yes, I can get it to fire the one round and lock back, i'm using gen 3 mapgul magazines currently. Replaced my ejector and extractor both with some results but still misfeeds.

I had a similar problem and my issue was a combination of mis-labeled buffer installed....was a 9mm buffer and not a 308 buffer.....and adjusting the gas block.