>>63957958The case probably wouldn't need to be *that* much shorter, just enough to put the neck around the bearing surface of a 75โ95gr bullet while maintaining a 40.5mm COAL. It'd be dictated by how much case capacity you could give up before you couldn't push the bullet to 1000 fps in a 10" barrel with 50 kpsi chamber pressure anymore.
A cartridge's center of gravity is always going to be a little fucky since the bullet generally weighs more than everything else combined, e.g., a typical .44 Magnum round consists of a 240gr bullet sitting in a ~110 grain case with 20 grains of powder in it. Again, I don't really think the magazine would care, since even if you made some deranged handload with a depleted uranium bullet and magnesium alloy case, there's simply no room in the system for the cartridge to spin out or whatever you're imagining it doing as a result of its uneven weight distribution.