View Full Version : Colt New Service,45 colt problem

May 10, 2010, 10:46 PM
I have a Colt new service with a four digit serial number. Colt says it was mfg. in 1903. Chambering is 45 colt. My problem is that the cylinder throats slug out at .451 and the barrel slugs out at .454. I thought the gun was all original.
What diameter bullets should I size my cast lead to? They drop from my mold at.454 I don't want to damage the gun but I do want to load and shoot it

May 11, 2010, 12:30 AM
You will never get that revolver to shoot straight in that configuration.

You will have to do one of two things...

1. Have the cylinder throats reamed to .454; or,
2. Rebarrel with a .451 bore.

May 11, 2010, 04:26 PM
Agreed, you will need to have the gun worked on to correct one or both of those issues.

Pre-WW2 45 Colts used a .455" bore diameter, post-WW2 45 Colts use a .451" bore diameter, so factory-loaded 45 Colt ammo often used/uses hollow-based bullets to expand and fill pre-WW2 barrels. FWIW, a new .451" bore barrel or a take-off barrel from a Colt 1917 revolver would screw on perfectly, allowing use of modern 45 Colt ammo with a reasonable expectation of accuracy.

James K
May 11, 2010, 08:37 PM
It depends a lot on condition, but installing a new barrel on a 1903 Colt NS might be nose-cutting. Those guns are bringing good prices in good original condition, and a barrel change will cut it in half. Reaming the chamber throats won't alter the value.