Hello,
I use to own a 7.5" Maximum. Still have about 200 handloaded rounds out in the garage for it, using 180gr XTP's. I was told to NEVER use any of that old Remington ammunition in it, as the powder used was of the ball type and would/could sandblast the topstrap. I used IMR 4227 (extruded) powder with WSR primers, and I never had any topstrap issues. These guns were given a bad rap IMO, probably due to badly put together factory ammunition. I have read that these guns should be used to push heavy bullets to magnum velocities, not lightweight bullets to mach 2, that is what does the damage.
Jared