You'll just have to try and see. I've shot .44Mag up to 1333fps and no leading with standard 15BHN hard SWCs when testing 2400. I know some use the harder Oregon Trail bullets at Mag velocities too. Never have used a gas check on any of my lead bullets.
A clinger. When guns are outlawed, only outlaws will have guns. Single Action .45 Colt (Sometimes improperly referred to by its alias as the .45 'Long' Colt or .45LC). Don't leave home without it. Ok.... the .44Spec is growing on me ... but the .45 Colt is still king.