I've loaded the .25-20 single shot using .25-20WCF data for several years for a Remington No.2 rolling block chambered in that caliber. As fortune would have it, I have had on-hand original .25-20 single shot brass that had been necked down to .22-3000 R2. I used the .25-20WCF dies to neck size the cases and seat the bullets. Works well. New dies in .25-20SS will cost an arm and a leg. If you do not already have .25-20WCF dies you may have a decent chance of finding them used at a gunshow, dealer or auction site. New brass manufactured by Bertram is available from several sources and that too is quite expensive. Good luck with the "new-to-you" rifle.
