The 25-20 Single Shot

 

The 25-20 SS has a relatively long neck, well suited for shooting cast bullets and is much easier to clean black powder fouling from than the more bottlenecked 25-20 WCF. The Winchester catalog of 1899, lists a 25-20 Single Shot load of an 86-grain bullet, cast from 1-60 alloy and pushed by 19 grains of black powder for a velocity of 1400 fps. In my own shooting, I have found that bullets cast from 1-10 alloy to be superior in accuracy with both smokeless and black powder. Small Rifle primers are adequate for all smokeless powder loads but Small Pistol primers seem to work better with black powder. That being said, the author has some vintage Winchester 25-20 SS cases that take Large Pistol or Large Rifle primers.

Modern Rocky Mountain Cartridge 25-20 Single Shot case on left, showing the Small Rifle primer and a vintage WRA 25-20 Single Shot cartridge with Large Rifle primer.

The somewhat hard-to-find IMR SR4759 smokeless powder works well in the 25-20 SS as does readily available Alliant 2400 and IMR 4227. When using black, 3Fg Swiss powder gives the highest velocity, coming in at 1335 fps. This makes the little .25 a very useful varmint rifle to 200 yards without the boom and thunder of the larger black powder cartridges.

Brass cases are currently available from Rocky Mountain Cartridge, LLC, BertramUSA and Buffalo Arms Company. The 25-20 SS is not readily formed from any other parent case, although R-2 Lovell brass (originally formed from 25-20 SS) can be necked back up and fire-formed to original configuration. Vintage Stevens rifles used a 1-13 twist, Winchester supplied a 1-14 twist and Remington rifles came with a 1-12 twist. My own Winchester Low Wall has a 1-12 twist Krieger barrel that has proved to be very accurate with bullets up to 110 grains in weight. When loading for vintage rifles, it is wise to measure the rim-cut on the chamber, as there can be significant variations as to depth, possibly resulting in excessive headspace.

Case Dimensions Are as Follows

•Case length: 1.63
•Base diameter: .315
•Rim diameter: .378
•Rim thickness (Original WRA brass): .050
•Neck diameter: .275

•Basic Black Powder Load:

•108-grain Saeco bullet, 1-10 alloy, sized .258, SPG Lube, .060 Walters Wad, •17 grains Swiss 1½ Fg powder, CCI Small Pistol primer, Bertram brass, .257 expander ball, slight taper crimp, OAL: 2.105.
•Velocity: 1270 fps.

•Same as above, but with 18 grains Swiss 3 Fg powder: 1335 fps.

Basic Smokeless Powder load:

•108-grain Saeco bullet, 1-10 alloy, sized .258, SPG Lube, cotton tuft on powder, 7 grains SR 4759 powder, CCI Small Rifle BR primer, Rocky Mountain Cartridge brass, .257 expander ball, slight taper crimp, OAL: 2.105.
•Velocity: 1429 fps.

•Same as above with 7.5 grains: 1490 fps.

•Same as above with 8 grains: 1580 fps.

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Caption- The 25-20 Single Shot cartridge flanked by the 25-20 WCF (left) and the 22 Long Rifle (right).

Photo credit: Sheryll Garbe

For the serious rifleman looking for an accurate varmint cartridge that is compatible with black powder and deadly on varmints, he should look no further than Mr. Rabbeth’s surprising little wildcat, the 25-20 Single Shot.