I'm curious.. I own a lot of Thompson Center rifles but never had a hammer crack. Where is this crack? If it is something like Lee said, where a good welder could braze it, then smooth it off for appearance sake, I wonder why that would not hold.

I might be wrong, but there was a fire at the Thompson Center Company many years back and they lost an entire line of equipmentand machines. I am wondering if that model rifle partof yours was not in that lost machinery. So they no longer had parts unless they re-tooled.