Well Tok, I just went "down the rabbit hole" with some of those videos. Several interesting videos I just watched and more to go back to watch later. I don't think most of us would come up with the idea of moving metal with a hammer vs. just filing off the offending "bumps/lumps".
Had to watch the Krag Jorgensen video, too (among others) as I once found the poor remains of an old Krag buried in woods behind my in-laws house. Figure it was used during a shoot out between moon shiners and revenooers during the fighting that went on up there during Prohibition. That area was called "Squat and Dodge" to this day due to the fighting. The saying way, "If you're going up there you better be ready to squat and dodge."