I wouldn't shoot any rounds that are too corroded to feed into the chamber with minimal force, but I would have no worries about shooting the rest of it. The main thing you have to watch out for is squib loads. Just make sure every bullet you fire leaves the barrel before you chamber another round. As long as you don't shoot a round with a bullet already stuck in the barrel, I doubt .22 ammo is going to do any damage to your Marlin.