My own AMT jamming issue was with my Longslide Hardballer, which I have lavishly fawned over, adding a compensator, Aimtech scope mount, panoramic reflex sight and new grips. Looks for all the world like a first class race gun. Drool. However, it worked like a government healthcare program - jamming constantly. When I bought it, it didn't come with an original AMT magazine, and not finding one at the time, I tried about a dozen different magazines until I found what worked. Not Wilson, not Colt, not Kimber, not Springfield, not Les Baer, nope -lucky me, I found that for reasons known but to Our Lord, who works with these weapons in mysterious ways, that inexpensive, humble McCormick and even more humble MecGar mags worked perfectly. Now my lovely Longslide is the envy of one and all -accurate beyond all expectation, reliable as sunrise, and with a "cool factor" that is no longer available from any manufacturer at any price.
Liam -your chambering problem is most probably your magazine but maybe your feed ramp needs a bit of polishing. Your extraction problem is most probably your (duh!) extractor. Together, you're right -you won't make it through a whole magazine without a stoppage. Get on the phone and call several local gunsmiths, find one who has experience with these guns, and let him have it. When I went to deliver mine for some work I wanted done, my gunsmith proudly displayed his own Longslide Hardballer, modified exactly as I had done mine except he had a red dot sight instead of a reflex sight mounted on his. Same mount, same compensator, same grip, etc. I knew I had found the right man for the job. Oh - he also had a McCormick magazine in his. Good luck.