Don't know what to tell you on the PMAGs, except the rounds are absolutely 2.275 and they fit and feed in my 20 round PMAGs.
I think PMAGs have been made in a bunch of OALs. The ones I have won't do anything over 2.260". I could swear I have heard of some that were even closer to 2.30" than 2.275".
I've had occasions where 3-5 rounds loaded long will work in a Pmag, but then they jam up if you load more rounds in the mag. I've never heard of an unmodified Pmag that will hold a full mag at more than 2.260" though, except for the "Six8" mags that were only for use in those specific lowers. Of course, some guys cut out the front of the mag to allow longer OAL; we had a discussion on that here last year IIRC.
Pretty cool if DW's Pmags actually allow a full mag at 2.275". I'd like to have some of those.
