Following up, the new magazine showed up today. It seems to feed various ammo types just fine. The feed lips on the new mag are a lot closer together than the one that came with the gun, and it seems to fit a bit tighter, and possibly hold the front of the magazine upwards just a slight amount more. Interestingly, the new mag is a matte finish on the metal, whereas the old one is a shiny blued finish.
I put an old Nikon 3-9x40 Prostaff on the rifle with some Burris Signature rings I had laying around, and added a YHM QD mount so I can stick my Turbo K on there. I'm giving the bore a good cleaning right now. I've packed a few things, and I may brave the heat to head out to some high desert peaks tomorrow morning, early, to beat the 100 degree heat and put a few rounds through the gun, and do some scouting of the area I'll hunt deer this fall.
I tried to tweak the fee lips on the old magazine, but so far, it still will always jam on the second to last round, jamming the nose of the bullet into the bottom of the barrel breech face while the rear part of the brass has not quite cleared the feed lips enough to pop free yet. I've also had rounds pop free of the mag and then get caught sideways in the ejection port. Its almost like some rounds escape the feed lips early and get flung sideways, and others get stuck, like the feed lips are not releasing soon enough. Strange issue for sure.