Ain't none. Just like the .38 S&W Special/Colt Special, same case, different name.
Technically, in the really old days it was a .25-21 Marlin, always trying to one-up Winchester. The only difference was the .25-21 was very slightly longer in the neck. The Winchester cartridge can be fired in either.
If you have more than one .25-20 or .32-20 you will notice that there is a noticeable difference in the fired cases, more than I have ever seen in any other cartridge with the exception of the other Win. dual use cartridges (.38-40, .44-40). For some reason the chambers were all bottlenecked, but a lot of old black powder period ammo was straight taper llike the .32-40 or .38-55.
Now you know more than you wanted to, enjoy it, it's a good find if in good shooting condition.
It's likely the same as a .25-20 Winchester, but a chamber cast will tell you for sure.
Actually the 25-21 Stevens is a short .25-25 Stevens. These are straight cases, and very long for their calibre. Just to muddle things a bit more, there's a .25-20 Single Shot which has a longer case than the Winchester. It was necked down for the 2R Lowell or .22-3000 Griffin & Howe, which was popular in the `30s & `40s. The 2R is just shy of the .222 Remington in power.
.25-20 Winchester - 1.330"
.25-20 Single Shot - 1.63"
.25-21 Stevens - 2.05"
.25-25 Stevens - 2.37"
Actually Winchester "borrowed" the .32-40, .38-55 and .40-65 from Marlin - Ballard. Check out Barnes "Cartridges of the World"
(Edited by Jack Monteith at 11:51 pm on Jan. 23, 2002)
Jack made a point and I realized I had gotten a step ahead. His comment about the .25-21 Stevens, etc. is correct, but had I said what I meant to it probably would have made more sense.
What I was referring to was the .32-21 Marlin. This is very similar to the .32-20 which can be shot in the Marlin chamber. The .25-20 Marlin likely had the .32-21 as a parent as the .32-20 Win is the parent to the .25-20 Win.
In either case, the Winchester cartridge can be used in the Marlin which was the original question.
A forum community dedicated to Sport shooters, owners and enthusiasts. Come join the discussion about optics, hand casting bullets, hunting, gunsmithing, styles, reviews, accessories, classifieds, and more!