This is all based on my faulty memory, but in movies, Clint Eastwood used on in Sudden Impact and Antonio Baderas had one along with one of the bad guys in Desperado. In the Death Wish movie however, Charles Bronson used a .475 Wildey, not an Automag. They do look a bit alike so the error is understandable.
From what I've read, the ASutomag was rather unreliable. Many feeding problems, although I think part of that was due to the quality of the ammunition. You either made your own cases from .308 Win., .243, etc which entailed a hell of a lot of work or you bought what scarce commercial ammo was available, most of which I understand was made in Mexico for AMP. I understand that quality range from way too hot to way too underpowered.
I remember the LAR Grizzly. LIke the Desert Eagle, you need a hand like King Kong's to comfortably handle one. I never was fortunate enough to handle an Automag.
On making AMP cases, IIRC, you gad to first run them through a cut and trim dddie, then ream fairly deep into the insides of the case then run through a full length die and finally trim to proper length. Sounds like too much of a PITA to me.
Paul B.