Colt New Service

[Johnny P]

The first Model 1917 Colt revolvers did not have a shoulder for the .45 ACP cartridge to headspace on if no half moon clips were available, but at about serial number 10300 Colt machined their cylinders to have a shoulder.

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Smith & Wesson Model 1917 Revolver.

[Allen]

I don't have access to the gun now so I can't verify the serial # range. We/I always used the clips for extraction purposes. I never tried it w/o the clips.

[Allen]

They came in a bunch of calibers.

"It was made in the popular large caliber revolver cartridges of the day: .38-40, .44-40, .44 Russian, .44 Special, .45 Colt, .450 Boxer, .455 Webley, and .476 Enfield."

+ the 38 long Colt, 38 spl, and 357. Then the 45acp on the 1917.

https://en.wikipedia.org/wiki/Colt_New_Service

[Johnny P]

The early Colts had to use the half moon clips as there was no shoulder for the cartridge to headspace on, but the S&W worked fine except you had to pick the empties out one at the time.