Just completed many latest build using a ARFCOM billet upper and lower receiver.  Tonight I was running mags through it and cycling the action to make sure everything is good.  My Pmags kept hanging up on the bottom of the magwell and not allowing it to seat.  It looks like the very last "rib" at the top of the mag before it goes into the magwell is the problem.  I haven't tried any other mags yet, so not positive yet.

Anybody else deal with this issue?

Which model Pmag? Gen2 or 3?

 

so far no problems here

Gen 3.  I'll grab some of my other generation pmags along with usgi mags and see if I have any issues.

So it's not the lower, is the ARFcom upper.  The outside of the feed lips is hitting on the id of the upper.  I tried a variety of different generation pmags and its a no go.  My USGI mags fit tight, but they'll seat, barely.  I tried a variety of dissent uppers and I didn't have any issues, so it's definitely the upper receiver.

I'll just have to contact them and see what they'll do.  Having a rifle that will only accept a small percentage of the mags I already own makes out worthless to me.