Greetings my dear Netizens....
from my notes, shamelessly stolen from all over the web, I have found the following information:
1ST & 2ND GEN COLT 20 TPI
3RD GENERATION COLT 24 TPI
Colt SAA First, Second and Third Generation barrel thread specification
The barrel shank and thread specification for the
first and second generation Colt Model P Single Action Army revolvers are:
Shank overall length: .699"
Length of threaded portion of shank (shoulder to breech end of thread): .580"
Thread specification: .695" x 20 tpi
The barrel shank and thread specification for the
third generation Colt Model P Single Action Army revolvers is:
Shank overall length: .699"
Length of threaded portion of shank (shoulder to breech end of thread): .568"
Thread specification: ..683" x 24 tpi
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USFA barrel threads & 1st Gen clones) are the same at 20 TPI x .695” + or- tapered thread,
3rd gens* are 24 TPI x 11/16” (.681” + or —)
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Uberti barrel thread spec 11/16" (.6875") - 20tpi,
Pietta barrel threads are metric and measure 18mm (.704" - .708") x 1.0mm range.
please feel free to update and or correct....