The wife has sort of got on my case about a few project guns that are hanging around and while one is a definite project (P14 Enfield English style medium rifle 375 H&H) the other requires a bit of thought.

The action is an 1867 Remington Contract model with the captive screw system and is in very good condition.

I already have a long range rifle (50-90) and a mid range (50-70, 12.17x44R) and while something in 45-70 would be nice, I know there is a barrel under the tree for my Prohunter.

I thought about a carbine, for when I go out riding or for those quick shots when in the thick stuff.

Caliber is kind of hard, since I don't really want to duplicate something I already have and would like to stay in a caliber suitable for medium game.

So any suggestions or ideas?

Thanks

In a carbine style Roller I'd be inclined to chamber for the .38-55 myself. I'm not a recoil fan, and that would be a little less recoil for me.

Would that be the Winchester Version of the 40-65? because if memory suffices Ballard had one as did Maynard and Sharps may have had a version (could be wrong on that one, but with Sharps you never know)

What barrel length would you suggest with the 40-65? Keeping in mind the idea of carbine or at least a friendlier horse mounted barrel length, shooting from horseback is more than likely during deer season, you can really get close to some big deer if they are use to horses and cattle being present (had to make a big hunter orange vest for the horse though it still doesn't like the balaclava )

Its my understanding that the bottle neck cases can be a bit more finicky  when working for accuracy, but that might be more of a black powder issue.

I acquired a Italian Sharps short-rifle/cum-carbine this summer that has been cut down and rechambered to 40-50BN .  I have not done much with it yet since it is iron sighted and my eyes do not do real well with irons. But it came with with a batch of PP bullets/5744 loads it seems to shot them fairly well and quite pleasantly  Its quite a fun gun to shoot and I'd feel confident with it as it is now on deer and 100/150 yards.

you might give consideration to the 40-70SS/405 winchester

I have aquired (2) 50-70 RB actions,with most interior parts.I will surely GO- BPCART.,what cart?I have no barrels;with these actions, so I am researching oddities for too shoot!! Any info,two cents past experiences will be great. ick Stack

Don't pass up the .40-70 Sharps Straight either. You can have the Roller chambered for the new Hornady .405 Win brass and use that cheap brass already formed, but load it to .40-70 SS loadings. 
No reforming, no expensive brass, and not hard on the shoulder in the old loads. This is what I used for my Remington Hepburn rebarrel.