Bruce, it is actually because of the "Short Throw" Lever Action Handle which affords faster cocking action and the 20" instead of the original 24" Barrel and longer lever handle.

Bruce - that would be because the Winchester 1873 was originally produced with a 24 inch barrel. It was dubbed the "yellow boy" due to the gold colored receiver. Then the 20 inch version was introduced, which was shorter, to make it easier to handle in brushy/woods environments and from horseback. It was therefore dubbed the "Short" rifle because of the shorter barrel.

Hey there user. This gun here is "The Gun that Won the West" Chambered in 44-40... 38-40... 32-20... 22 LR. Hope this helps