Colt New Service serial number dates to 1915. Its original unshaved cylinder is chambered in .455 Eley. Frame bears Canadian crossed pennants proof mark. Barrel was professionally shortened to 2-3/4" and sight remounted long ago. The gun weighs 36 ozs., about the same as a .38 Special Official Police.
Interestingly, USGI .45 ACP hardball headspaces against the .455 chamber cone. The case heads stand just proud enough for the hammer nose firing pin to reach. It reliably goes bang with ACP ammo and shoots close to the sights with center of mass hold at 25 yards. Shots are slightly left, but mostly stay in the bull of a B8 repair center. I use a BIC pen to poke out the .45 ACP brass.
No moon clip is needed for .45 ACP and wouldn' t fit anyway due to the unshaved original .455 cylinder. Use of .45 ACP ammo I view as a commonly available, emergency expedient, rather than for steady use. I have an ample supply of Fiocchi .455 Mk2 brass to reload and an Accurate mold 45-264H
flatnosed bullet which matches service velocity with 3.5 grains of Bullseye. While the catalog drawing shows .452", when you order a mold from Tom you can specify your casting alloy and the diameter you want. My mold drops .455 as-cast from wheel weights. I load them as-cast and unsized, lubed with 45-45-10 from LSStuff.
Fiocchi 262-grain factory lead ammo groups well, but POI slightly left. Sandy Garrett at NoVA Gun Works will correct that turning the barrel a bit in the refurb. Plan is to set barrel back to reduce B-C gap to 0.004", correct end shake and timing, then matte blue. I figure $400 in gunsmithing to restore a $400 bargain.
Normally any shooter grade Colt New Service brings $1000+. I got this one cheap off Gunbroker because the Bubba' ed gun had zero collector value and the original grips were broken. I got a set of nice replacement grips from NC Ordnance which are a faithful copy of the originals. The BK grips adapter for the Army Special and Official Police fits the New Service frame. To me it is worth the cost of gunsmithing to have my Carhartt Barn Coat pocket blaster. And NO - I will NOT Fitz-butcher it!
The Speer 250-grain Deep Curl JHP with 4 grains of Bullseye gets 650 fps, expands well and stops in 4th gallon water jug. FC65 M1911 ball gets 700 fps in the 2-3/4" barrel and stops in 6th jug.