I have a M65 Winchester .25-20, and gave a M92 carbine in that interesting caliber to my #1 son years ago. We load for them both, mostly Lyman's excellent 257420 GC, cast from air cooled wheel weights with a pinch of tin for fillout. IMI 4227 at 8.5 gr's is a good load, doing close to an inch at 50 yds with a peep sight, as is Win 231 at 4.3 gr's. We've had better luck with WSP Mag primers or WSR's with both powders too. Sized 0.259" and carefully culled for defects, that bullet is all you need.
With any of the lead alloy bullets, commercial or home cast, a light coating of Lee's Liquid Alox, swirl lubed may cure any leading tendencies. It's worked for us in both pistol and rifle cast loads. Too...with our .25-20's, a light, very light, taper crimp improves accuracy dramatically. In our use, neck tension has been more than adequate to prevent bullet set back from the .25-20's light recoil while in the mag tubes. That taper crimp is little more than removing what ever belling was done to allow seating. Carefully done, a very limited roll crimp can do the same.
When Midway was reducing its inventory, some years back, I bought 1000 of the old Remington 86 gr SP, and have used them sparingly since. It's a bit on the heavy side, I've always thought for the caliber, but shoots as well as the Lyman cast 257420 GC. With 4227, 9.5 gr's gives me a chrono'd 1640 fps with excellent accuracy. Mag pistol caps or Small Rifle do better here as well.
While I've worked with Speer's FP 75 gr. and Hornady's 60 gr FP, neither was quite as accurate as the above two bullets, but just by a smidgeon. 4227 & 4759 both worked ok with these two.
Lastly, RCBS' Cowboy bullet, a plain base, flat point @ 85 grains, is another alternative. Cast 1:3, of Pb to wheel weights and sized 0.259" for our two Winchesters, it'll do sub-2" gps at 50 yds with good loads and carefully culled bullets.
HTH's, and BTW, you can reform .32-20 Starline brass to .25-20 fairly easily. My loss rate is less than 1per25.
As is always the case: these are my loads, safe in my guns. If interested, always consult a GOOD manual, & consider the pressure implications for the age and condition of your guns, before working up to them.
Rod