Have you tried the updated mags? They changed the follower to address some issues with 6mm rounds
I have, and unfortunately I still get stovepipes (nose down) with my 6GT in my AT-X.
The only work-around that I've found at this point is to load the rounds forward...even with the back of the feed lips. Feeds great then, but I doubt that would work well if I were running around in a PRS match and slamming my rifle off of stuff (getting rounds to shift in the magazine).