Colt New Service M1917 .45 ACP chambers

[Outpost75]

I examined today a 1918 date of manufacture Colt New Service in .45 ACP. Its bore slugs .443", groove is .451", cylinder throats are .456” Cylinder gap pass 0.007”, hold 0.008”

A 1914 date of manufacture .455 Eley has bore .444", groove .454" with cylinder throats also .456"

A 1923 date of manufacture .45 Colt has similar bore, groove and cylinder throat dimensions to the .455

Attachment 238505

The chambers of the .45 ACP Colt New Service have EXACTLY the same dimensions as my 1914 date of manufacture Colt New Service .455 Eley, except for the difference in chamber length which resulted from the .45 ACP cylinder being faced off at its rear to clear the moon clips. It is quite apparent that Colt used leftover .455 cylinders from its British revolver contract and simply machined additional head clearance on them for the moon clip and changed the dimension of the frame lug to correctly position the cylinder.

Attachment 238506Attachment 238507

When .45 ACP Ball ammo is inserted without clips it drops goes all the way into the chambers, stopping with the case heads flush with rear of the cylinder, the case mouths coming to rest against the chamber cone.

Contrary to common Internet lore, the .45 ACP New Service chambers were NOT bored “straight through”, as they have a normal angled transition from the case mouth in to the .456 cylinder throats, which is evident in the photo.

Colt M1917 revolvers which were reworked for WW2 issue have the square stop surface to permit headspacing .45 ACP rounds without using the half-moon clips. Later WW1 guns will also have the purpose-built .45 ACP cylinders with the square stop surface, as the supply of leftover .455 cylinders from the British and Canadian contracts, which could be faced off, was exhausted.

[WehrmannsGeweher]

Good info. Love my CNS revolvers (3) ! 38 (Factory conversion from 455) 44 spec (factory nicklel), 45 colt match (this)

[Randy Bohannon]

Gorgeous 7 1/2” N.S. I sold a Colt Anaconda for crazy money in 45 Colt to get my 4 1/2” N.S. In 45 Colt. The only better Colt double action is the Shooting Master,not the Python.

[WehrmannsGeweher]

Yup, I'm bidding a SM 357, a 7.5" NS in 455 and a 4.5" 38 S.

None are cheap but a bit less than a mint Python.

[Randy Bohannon]

You’re going after the good ones, 455’s are getting harder to find that are original. Thanks to Starline you don’t have to rechamber to use them.
A lot of hearts went pitter patter when the 4 1/2” showed up at our local LGS and I snagged it. The 4.0” barrels the rarest with the 4 1/2” next.

[Outpost75]

My .455 is the favorite. Tom Ellis at Accurate cut 45-264D to fit this revolver. Bullets drop .456" in 1:30 tin-lead from Roto Metals at 265 grains This slug also works in the .45 Colt if you have a revolver with cylinder length which can handle 1.68" overall cartridge length when the long nose is assembled into .45 Colt brass.

In my .45 Colt New Service I trim all brass to 1.275" and use 6.5 grains of Bullseye. In Colt SAs having shorter cylinders use Starline .45 Schofield brass with 5.5 grains of Bullseye.

In Starline .455 Mk2 brass I use this bullet with either 3.5 grains of Bullseye or 3.7 grains of 452AA, which I still quite have alot of, leftover from Camp Perry bullseye shooting days in the .45 ACP. Velocity from the New Service 5-1/2" barrel with 0.008" barrel-cylinder gap is 700 fps, a "full charge" load which very closely approximates that of new commercial Fiocchi.

Attachment 238543Attachment 238544Attachment 238545Attachment 238546

[johniv]

Good info, thanks. My 1917 Colt is similar, as loose rounds drop flush with the rear of the cyl.
John

[Harter66]

Mom's 1917 Colts is a 1918 by the USA SN but is a 1915 by the frame number , I guess the Colts authorities say it makes a difference . It correctly HS on loose ball and I have fired a few as such . It actually will hold the the clips floating on new brass . It has .454 throats into a 452 groove . It's been shot a lot . It has .003-6 on the breach end depending on the particular case new AR give .004+ , .005 is crush fit and too tight . That leaves .006 up front but even that is full contact tight . I'd call it .0045 and .0055 . The Smith I had was .004 on both ends with new AR cases but I could only get that if I did each end separate otherwise it was .007+ gross . That Smith was August 1917 mid month so it's unknown if it was assembled under S&W or the USA as the Army assumed production control 8/17/18 . The Colts I didn't track down that far as it was rumored to have been a Johnny Cash gun , that was likely for "artistic license" in story telling because the assy numbers match .
The Colts does shoot heavies better than the Smith did .