Consider that the cylinder gap of any revolver effectively focuses a cutting torch flame up into the top strap area each time the gun goes off.
Consider next that the higher the energy and longer the driving duration of this flame -- the greater the cutting action of this torch.
Consider last that the very factors that make for high velocity of heavy bullets are high energy/long duration of the propellant's action.
Bottom Line: It isn't so much that "ball powders" per se, are hard on the gun. It's the fact that the powder's doing what we ask
-- and there ain't no free lunch.
Unless you're a Democrat, of course.