"This is assuming you're talking about engagement surfaces on hammers & triggers, not trying to make shiny jewelry out of a MIM part."

You assume correctly, Denis. I am asking about engagement surfaces that come into play for action/trigger jobs.

Thanks, guys. All of you in one way or another have confirmed what the gunsmith told me.

"I've been designing and building industrial machinery for a lot of years and if you have gibs and ways that have become fully polished by use they will then start to gall rather quickly..."

scooter, you must mean a type of steel other than pre-MIM traditional steel for internal engagement surfaces, right?