Looked through the 5 pages here, nothing similar to my question so need to ask...why?  It's a new build (Anderson pistol lower, Aim Surp bcg, BCM ambi-c.h., and a PSA 10.5" upper) that, otherwise functions just fine with or without my SRT can.  

Probably have only run 300 rds through it thus far and this has me stumped.  Any ideas, guys?

Does it stay open if you manually cycle it?  If so, try a hotter round.

Thanks for your reply, Mousegun.  Yes, the bolt stays back when manually cycling with a mag inserted and no, without a mag inserted.

So far have run 3-4 mags with the last of my old Guatemalan surplus 5.56 and 5-6 mags of fresh Wolf Gold with same results...no joy.

Does this happen when firing with several mags, or just one?



What buffer and spring are you using?



Did you lube the bolt/BCG?



Also, check to see if the gas block is loose or canted significantly to one side, and check to see if the gas key is loose on the bolt carrier.

Your buffer maybe too heavy. Also check your gas block & make sure it's aligned properly. Another problem maybe your bolt catch. The nub on it may sometimes not have enough contact w/ the magazine follower. If that's the case,  a seekins precision enhanced bolt catch will fix that issue.

I'd strip and clean the heck out of the BCG if you haven't already done so... even then I'd do it again.

Make sure the key on the BCG isn't dragging on the gas tube by removing the bolt and let it slide into the upper. If it bumps, its probably dragging.

Check your gas rings on the bolt to make sure the breaks in the rings are staggered.

Last, as mentioned above, make sure the gas block port is aligned with the barrel gas port. Make sure no gas block gas leakage.

My PSA 6.8 kit had issues ejecting. Much better after doing the steps above. Good luck.

Thanks, again, gents, for the replys.  Good suggestions.  Much appreciated.