Well... if you've read enough forums (and of those that are out there, I'D read M4C and call it a day. I'm a mod at another forum, and I go to M4C when I need the STRAIGHT dope!), you KNOW that BM and DPMS both have their share of "issues." An out-of-spec lower is not beyond the realm of possibility, and switching over to Colt boltcatches still might not make your pinholes line up correctly, for instance.

I had a factory new Gen.III POF lower, that STILL had problems with early PMags sticking, and even Rev. 'M' mags wouldn't drop free, so poorly spec'd lowers are NOT limited to your cheaper brands. On the other hand, my BCM lowers eat EVERYTHING, which is probably why I have them in three of my four 5.56 rifles at the moment.

I don't have any mag-in-lower pics at the moment (I'll see if I can't snap one soon, of my STS Arms lower with a mag - I'm waiting on a custom upper still to arrive for it), but it might be worth having a competent 'smitty look at your lower, and see if its the mag, or the lower. Bolt catchs are the ultimate PITA when it comes to DIY - I'd never feel bad about spending money to have one installed RIGHT!