There are bullet moulds available for at least up to 250gr. A lead bullet might foul a gas port though, if that rifle uses a gas port - likely not a blowback action, but I just don't know either way.

.41 mag bullets run up to 220gr. Speer but in a large semi-wadcutter-type lead nose that might not chamber on autoloader function, but the other makes here, are maxed at 210gr.