Good luck bending the lips in a bit, I expect it to be a trial and error process. I suggest you make up some dummy rounds (hardball bullets) to use during your testing, so you don't batter live ammo.
Once you get the dummies feeding properly (by hand), then try some live ammo and see if it works.
Good Luck, I really hope you can get it running right.
(and you do know, Murphy being Murphy) you probably won't find a spare magazine until AFTER you get yours working!