Thats my concern also , a lot of the rifles in the 80s were very nice rifles ,but each one had its own mag.
On anything in a 308 lots of people say the FNH Mag ,but the M14 Mag is a far better Mag ,stronger ,cheap , and it is now offered in a 25 round that is only 3/4 of an inch longer than to 20.
the 7.62x39 mag was designed from the ground up to work in any weapon that took a NATO/STANAG type magazine. C-Products didn't go through all the trouble to test and produce x39 mags just for the XCR. There are other companies out there doing x39 in ARs as we speak. I can't think of who off the top of my head but I remember hearing there was a huge demand for x39 mags for ARs.
Yes you can, that said most don't work worth a F**K! I have owned a Colt 7.62x39 AR-15 Upper for years. I have purchased many mags for it and most have problems. The more rounds in the magazine the more chance of a jam. My take ,,,, part follower and part "curve" of the magazine. I have a bastard AK/AR-15 weld that works great. Just looks funny as shit. Note the new C- products has one hell of a curve on it. I hope C products comes out with a good 15 & 20 rounder that works. :2cents: