Rather than weld it up, why not soft-solder in a ring instead? There would be a little mechanical stress on the ring during chambering, but that shouldn't be a problem with tin-silver solder.
You don't want silver solder as it's melting point(1200�F) might very well compromise the heat treatment of the bolt head. I would use 96% tin-4% silver solder which melts at about 500�F and is very strong.