GIVE a man a fish and you feed him for a day. TEACH a man to fish and you feed him for a lifetime.
SADLY, most fishermen are afraid to touch the worm.
The PT1911 is an EXACT copy of the 1911, albeit completely manufactured BUY Taurus. What this means is that ANY accessory part for any 1911 will fit the PT1911 without a problem. This tells us that the PT is NOT metric right from the start.
So, to start your search for a set of SS stock screws, go to brownells.com. If they don't have them, no one on the planet will.
Note that you'll likely not find a part listed "for Tauraus PT1911", but for "1911 style pistols."
