Bought a new Clymer .25-20 reamer from someone on this board, no complaints, good price, fast ship, etc.

When I got to looking at it, my thought was why the hell is there no leade, and why is the neck so long. So, did some looking and found the reamer spec. The reamer cuts a chamber with a neck .040" longer than the cartridge has. What the hell is up with that? Am I going to have to have this reground before I can effectively use it, or just pass it on and get a correct custom one made that actually fits the brass?

Anybody got any insight into why this chamber would be standardized like that?

That's the old factory Winchester chamber spec as they used lead bullets to start with. I have a Clymer 25-20 finish reamer that is the same way

The Cylmer 32-20 finish reamer I have is also the same type of longer neck no throat like what we are used to.

JW

It is a relic of the black powder cartridge era when chambers had no throats; but either used bore diameter bullets, sometimes protruding almost entirely into the rifled bore and barely seated into the case (many of them paper patched), or, in this case, the bullets are short and there isn't room in a 92 magazine for a longer one. Chamber designers of the era did not see a need for a tapered leade/throat.
In the former situation, the black powder impulse obturated the bullet to groove diameter.
Once smokeless powder (and jacketed bullets) was developed, that situation did not occur, and bullets started being groove diameter. Hence the adoption of tapered leades and throats.
You will note that other reamers made to original specs, like the 45-70, also have no throat; just chamber and rifling. I have those ground to my specs, as you seem to want.
Your reamer is not broken; just made to 19th Century rules. But if you want one made to modern specs, you can just have yours re-ground.
Also, don't forget that there are two 25-20s; the WCF and the Single shot, which has a case length of 1.6.
Standard one is 1.33, or supposed to be.

I actually prefer the no throat reamer, I usually use a throating reamer to fit the leade to the intended bullet. The odd piece is the extra long neck. That makes no sense from a lead bullet standpoint, the bullet obturates into that space, and then the abrupt chamber end swages it back down to squeeze into the bore, and the bullet is deformed all over the place in the process. Not good for leading, accuracy, or brass stretching.

Quite aware of the SS vs WCF, the SS is once again dead since the supply of Jamison brass dried up. You can't trust winchester barrel markings because they used the ss designation for both cartridges at different times, on their low walls.

I'll probably just have a custom reamer made up if I want to make an accurate 25-20, I've done that on a lot of reamers to fit what I want to do.

This has got me curious now, I have a low wall that I had lined by Redmonds 35 years ago, I wonder if it has the long chamber. That could explain to some extent why it's not particularly accurate. I always blamed the Redmond liner, maybe it's more the chamber. I'll go look at it and see.

When. SAAMI drew the prints, who knows what they used for reference. I don't have any original Winchester barrels to check.
Guys shooting 92s never noticed and shooting jacketed bullets, they would never know the difference.

I also have a Clymer 44-40 finish reamer the same way.

Am starting to plan a Win Low wall in 25-20 WCF and like you most likely have the neck reground and come back with a throater to create a normal lead.

JW

Most cartridges are allowed a minus .020 on brass length and a plus .015 on chamber length; that alone could potentially result in a .035 mismatch, and the 25-20 is more than that.
Most shooters have no idea how misfit their chambers and ammo really are (of course all AR members know), and how lucky were are that anything fits.
Add into the equation, reloading dies from several makers too, all with their own specs.
Amazing anything works.

Many things don't either.

George