Seeking a slick bullet for the Cimarron 1885 in 38-55 Win has been a fun exercise. I do however have some questions for those of you who have paper patched for this caliber, as well as those of you using this caliber in the CBA Matches - either as a PP or a greaser.
The Cimarron (Uberti) 1885 rifle has a bore of .373" and a groove diameter of .379". It also sports a rifling twist of 1:18 inches. This twist rate is conducive to heavier than usual (lever action) bullets of a longer length. A 310 - 324 grain bullet at about 1.1 to 1.3 inches is just peachy for that twist rate according to the Greenhill Formula, using the specific gravity for pure lead. The twist rate varies slightly depending on the length of the bullet from 1.0 to 1.3 inches. Rates of 1:17 to 1:19 can be had with slight bullet length variation. Let's simply say that 1:18 is an "optimal" Greenhill Formula result.
Slick diameter is irrelevant to the calculation since a bore slick (.366) wrapped to .372, or a groove slick (.372) wrapped to .379 will BOTH be spun at the .379 diameter prior to exiting the muzzle and the PP spinning off.
So we have a bullet of about 320 grains at 1.2" in length being spun by the "ideal" twist rate of 1:18 for optimum stability
Why then in our matches do we have shooters who have 38-55 barrels with twist rates as fast as 1:12" shooting 323, 325, and 331 grain bullets. If the twist rate renegades Barry Harmon, John Lahman, or Tom Acheson are reading this post, please educate me on why your twist rate differs from the "optimum" rate specified by the Greenhill Formula.
By the way to all readers. There is a WEALTH of information contained in the CBA Match Reports included in The Fouling Shot. If you are not a CBA member, consider joining us and receiving The Fouling Shot for you enjoyment.
With rifle in hand, I confidently go forth into the darkness.