They could be, I've been doing some study, the old trapdoor Springfields had bronze firing pins, I believe I found a reference to aluminum bronze for firing pins from 1912, They were cast, then hot forged. Many things I thought were kinda new have been around quite a while. Brass would most likely be too soft, though I'm finding out how ignorant I am in this study.
CNC produced 416 stainless triggers to replace the plastic triggers on Colt Mustangs, Mustang Plus II's, MK IV Government .380's and Sig P238's and P938's. Plus Colt Mustang hardened 416 guide rods, and Llama .32 and .380 recoil spring buttons, checkered nicely and blued.