I have heard some under the opinion that one of the favored weapons of Confederate cavalry in the west as under Forrest was the double barreled sawed-off shotgun. However Forrest used his cavalry much like mounted Infantry, so I don't see that the sawed off shotgun would have been much use in that role. I do know in some cases in the Trans-Mississippi the Confederate cavalry could not readily obtain proper carbines, so they would saw off the barrels of regular musket to make them a useable lenght.