Did a build with a NIB Roggio Arsenal lower.  PMags, both old and M revision will not seat in it and are near impossible to pull out if you bump them hard enought with heel of your hand to get them to latch.

Magazine would not go up far enough to have the bolt carch the rim of cartridge.  Caught the cartdige about about 1/2 way up the case and, of course, jammed.

All other metal mags worked fine, Old mil-specs, CProducts, O-kay,  etc. No jams at all.