Cartridgecorner - is your round with “AM” headstamp a 7.62 x 39 conventional cartridge? You did not mention that. If so, do you have documentation that it is made by Airmunition? I have several 9mm Airmunition items in my collection, and the “AM” 7.62 x 39 in question does not reflect the quality of manufacture of those items, or for that matter, Swiss ammunition in general.
If you are going just by the initials on the headstamp, I would have to doubt the identification of that round as being from Air Munitions. Of course, documentation settles the issue.