A great small game cartridge. I believe a better choice is .256 Win Mag. Why? Better brass and easy to form from .357 Mag, You can load it to higher velocities than .25-20 if you like. If you load .25-20 to the "high speed" load level you will likely find that you will trim fairly often even with a close chamber. The .256 has a short neck but this hasn't caused me any trouble with 1500 fps cast bullet loads. My initial 50 cases were probably loaded a dozen times each working up max and mild cast loads. No losses and I don't believe I've had to trim them. As much as I like my Sav 23 in .25-20, I'd like it better if it were a .256. I had a 10" Contender barrel but wanted a carbine, not being much of a handgun shooter. I have a chambering reamer and a barrel blank but haven't had the time to stub a donor barrel yet. I did barrel a Highwall for a friend and chambered it for .256 - he really enjoys it and doesn't worry about losing a case now and then in the field. Since you have to cut a chamber, you might consider the .256. The only improvement I can think of would be a longer neck, maybe .325 or so. I believe there are some .25 cal wildcats based on the .357 Maximum case but unless you want some faster jacketed bullet loads they probably wouldn't be of much use. Souns like a good project!