yes While I am not an owner of both, i posed the same question back on GT at one point, and MrApathy assured me that they are the same mags for the M and MA1.....and as he knows more about these guns than pretty much anyone i have run into so far....i'm gonna believe him.
people HAVE used them interchangeably. I just got a M9A1 mag in the mail today and as soon as I unpacked it and dropped in the range bag I can only tell them apart by the lack of wear.
Sweet! I'm glad to hear that the magazines are probably interchangable between my M-40 and the new MA1's. Just another reason for me to purchase one.