congrats on the 25-20! Sounds like a pretty fun cartridge!
If you find accuracy isn't great, clean your barrel out super good and try jacketed bullets. they can be more forgiving if the bore isn't perfect.
I have a 32-40 with a less than perfect bore and it shoots jacketed bullets great.
as far as your 'next rifle' options, i'll have to say, I like your style. I too am attracted to the uncommon / obsolete cartridges.
I agree - that your next rifle should be in that ballpark - something in a 30-30 length action.
32-40 is a great option, especially if you like paying a lot of money for old worn out guns, haha. like I said, I have one and really like it. especially if you can get one with a nickel steel barrel, you can load it up for deer. Here's mine
the 356 winchester would be a much more powerful cartridge and would only be available in "newer" guns (old guns compared to now, but super new compared to a 32-40)
Other options to consider.
38-55 - probably "better" in many ways than 32-40, but the one challenge is that over the last 100+ years bore diameters have fluctuated from .375 - .381+
or if you could go 375 winchester - which is the new version of the 38-55 and is an older brother to the 356 winchester in that it was released around the same time for the same group of winchester 'big bore' rifles.
32 special is cool and fun
35 rem is great (but not if you want a winchester).
I guess depends on what kind of rifle you want. and what style. if you like the old style classy winchester rifles like your 25-20, then you should look for a 32-40, 38-55 or even a 25-35. If you want a newer carbine style winchester rifle, you could look at the 375 or 356 or even 307 winchester. or if you want a marlin, you could look for a 35 remington OR one of the cool newer marlin rounds like the 308 or 338 marlin express. those are thumpers. OR........... you could go to the lever darkside and get a 250-3000 or 300 savage in a 99 or 1899............if you want a scope, get a marlin or savage. or a newer winchester, but......ew........don't do that...... (jk)
obviously, the most logical thing to do would be get a 30-30, which you can get in any of the above styles and makes of rifles, and its almost the only option if you don't want to reload for it. in theory, some of the above cartridges are still factory loaded, but good luck with that these days.
Here are a couple more of mine.
375 big bore - regret selling it
35 rem
300 sav
1903 30-30
2003 30-30
I don't have any pics of any of the others yet......
Then............. once you get something (or a dozen somethings...) from the 30-30 class, you need to step up to the big boys...... and you could get a cool classic rifle like a winchester 1886 or a newer marlin in 45-70 (some guys here have some beauty examples). the only two "big" levers I was ever interested in were the .444 in a marlin or the 348 in a winchester. Just got a 348 this year, so I'm all set! I have a really bad shoulder so I have no desire to shoot the heavy thumpers for fun. Other possibilities would be, 450 marlin in a marlin or if you really go to the dark side of lever guns, you could get an 1895 in 33 or 405 winchester. All I need is the one rifle from this group. here it is my 348 compared to an old 1894
