Okay, back from the range. I got less range time with my M14 than I wanted due to having to get a bunch of stuff done with my Garand (set up adjustable gas system and sight in scout scope), but I did get to put two boxes of ammo through the M14 with AIA Enfield mags.
1 Box of Federal Power Shock 150's (what most everyone uses) - 0 FTF
1 Box of Musgrave 150gr RN (looking for trouble, but WTF!) - 2 FTF
It's a pretty small sample, but other guys are also getting out there and trying the mags and posting. I know I was looking for trouble even trying round nose bullets in my M14, but I had an old box that needed firing. The mags worked perfectly with the Federal stuff, and one failure per mag with the RN stuff. I honestly feel it's all to do with the RN bullets and not the mags. Although my number of shots was small, personally I'm convinced (based on what I shot and other posts by the rest of you) that we've found legal 10 round mags that work in the M14 without any modifications whatsoever. I'll be calling anyone selling these mags next week to try and scoop up a couple more. Man, am I happy!