Originally Posted by Utah Shotgunner
Raimey,

Will slug the muzzle later today. Will also double check for bore diameter marks.

Date is 1918

Date is 1918....or 1913. wink
Roll the barrel under the light and a strong case can be made for both. I filled the stamp with a white grease pencil and still cannot decide if it is a '3' or an '8'.

Bore diameter is .261"
Measured by driving a soft lead slug into the muzzle.
Eight wide grooves with very narrow lands.

Rim diameter is .510" if that will help identify the cartridge.

Mike