And with really old guns, sometimes parts from reputable places can be off dim or spec.
Ex: maybe shop XYZ has a bag of firing pins for some obsolete shotgun. They even came from long out of business factory that made the gun, correct part number too.
Good deal right?
They might have been factory seconds, maybe not to some spec (maybe heat treat or alloy).
Pay 15 bucks to have some little pin shipped, pay a 'smith to put it in and watch it break in a couple of shots. Then the owner brings it back to poor old 'smith and demands it be fixed right, for no additional money.
Ya know, since the shotgun was grandpa's and it's priceless (that'd code for: I won't spend over 20 bucks on it).
Heck, even if fixed the owners may not show up to get it for yrs.
And our poor 'smith becomes a junk gun "collector".
Ya really gotta watch it on old rigs, have customers with sense and wallets if you want to fix 'em. Amazing how guys with 50K trucks want their crap guns fixed, with top notch work, for pennies.
Heard it too many times.... if a guy wants that, and then questions my abilities in a rude manner (ask away, but don't be a d*ck about it)...........I just smile and hand him a card, with the number of a local hack that mangles guns.