Welding Gun parts
I am a retired welder, heat treat tech, NDI Tech and electro-plating Tech, that said, After I retired I went to work at a local Gun Shop in Lancaster CA. I worked sales and did all the shop welding for George Copland our Gunsmith. I have repaired more firing pin, pins, hammers, trigger etc than I care to remember. Normally I would agree with the opinion that its better to buy a new one, but is the parts are hard to find then you make one (cost is high with labor rates or repair the old one. A TIG welding machine is the best choice, the hard part is picking the right filler rod.
I settled on Brownells High Nickle rod, best all around rod for gun smithing. 1st, anneal the part (remove heat treat, weld repair, fit and function test and re-heat treat (a Rockwell hardness tester is good to have if you do this kind of work).