Here is a quote from a thread that I found at "The Firing Line" forum. This explains the difference between a rifle and a carbine so far as Winchester was concerned. The discussion refers to a Model 1894, but I had always read that this applied to virtually all of Winchesters lever guns with tubular magazines. Basically if it had barrel bands it was a carbine. If it had a crescent butt plate, a fore end cap, and a dovetailed magazine hanger it was a rifle. If it had these latter features and a barrel of 18" or less, it was not a carbine, but rather a "short rifle". But as the discussion noted, Winchester offered many options. So here is the quote followed by a link to the discussion.
"Differences between a Winchester rifle and carbine
In another thread started by PAHOO, a question was asked what the differences were between a Winchester model 94 rifle and carbine. In the spirit of education, I will describe what the differences are. The 94 action stays the same and all action parts are interchangable. A carbine which most are familiar with, has a normal barrel length of 20" maximum and can be as short as 14". All carbine barrels are round, no exceptions. Most carbine buttplates are flat "shotgun" type, made of either metal or plastic. Early carbines had a curved metal buttplate similiar but not the same as a rifles cresent butt. A carbine had a band that went completely around the barrel and forend that holds the forend on. The magazine tube is held to the barrel by the same type of band. A RIFLE has a standard barrel of 26" but could be had as short as 18", these were known as short rifles. Barrel could be ordered as long as 36", these were known as extra long rifles. Barrels on rifles could be either round, octagonal, or half round and half octagonal. A rifle was issued with a curved steel buttplate called a cresent butt. The forend is attached to the barrel not by a band but by a metal cap screwed to a dovetailed wedgemilled into the bottom of the barrel. The magazine tube is attached to the barrel not by a band but by a hanger dovetailed into the bottom of the barrel. Of course Winchester offered many options, however these are the difference collector recognise."
http://thefiringline.com/forums/showthread.php?t=481875