Regarding the DPMS mags. On my rifle, the locking lugs on the bolt contact the leading edge of the magazine follower, gouge into the plastic follower and will not let the bolt move to the rear. This only occurs when the magazine is empty. It appears the angle of the forward edge of the plastic follower on the DPMS mags is much sharper than the pmags.
On another topic, my SR 762 purchased in Dec. 13, absolutely would not run. A failure to fire happened when the hammer fell and there would be no mark on the primer. I had many failures to feed because of the bolt not moving to the rear far enough to pick up the next round. Experimenting with the gas regulator brought no joy. After several frustrating hours on two different days at the Range with only 55 rds fired downrange, I gave up and returned it to Ruger. My LGS who handled the return said that Ruger was able to duplicate the malfunctions and were sending me a new rifle. I was not surprised since my experience with Ruger's customer service has always been outstanding. I picked up my new rifle a couple of days ago.
While my rifle was "away," I picked up two DPMS mags. When I received my new rifle I tried the mags for fit and discovered the situation with the angle of the plastic follower interfering with the locking lugs on the bolt. I have not had a chance to go to the range with this new rifle yet but am looking forward to it.
mt