Wally ;

You omit the origin of your hammergun, but I suspect it is the UK. "rearrange the metal structure so that it will be strong again and not fail in the future" is a Star Trek option not yet available.

Buy two new hammer blanks and fit them or have them fitted. See below suppliers.

Stephen Howell


https://www.peterdyson.co.uk/acatalog/English_guns_and_rifles_hammers.html

https://www.blackleyandson.com/acatalog/English_Flat_faced_Percussion_Hammers.html