This OSR phenomenon that's referred to. Is it visible down the length of the barrel? If so, I have a hard time accepting that it's caused by the bullet. Even a "hard" bullet like a mono solid. You take a solid copper bullet, banded or otherwise. When that sucker hits the rifling in a considerably harder steel barrel, it will swage down to bore dimensions in pretty short order. Metal has to move period, or it would be a bore obstruction. Once the initial swaging is done, I fail to see how it could act on the barrel any differently than any other bullet, for the remainder of it's trip down the bore. Fire a conventional solid, and a monometal solid down the same bore, and measure them. See if there's a difference in the land/groove dimensions?

Jeff