I don't see muzzle damage as an issue at all. I know that I leave at least 3/8" of leather past the muzzle of my open toe holsters.

Starting in November, I will be hunting with a muzzleloader and carrying this $2500 engraved Open Top in the open toe flap holster shown, primarily sitting on the ground in a turkey seat. If I thought the open toe was going to present a danger to this prized sixgun, I would've done a sewn plug.