From a pistol barrel lenght,to a small carbine barrel lenght you will increase vel,enven with modern day powders.But jonly to a certain pinnacle of vel within the cartridges limits itself. For instance a 357 mag pistol with a 4" barrel will shoot like 350 fps less than a 8 3/8" barrel with a max load, and some more will be appericated with a short barreled rifle,but not much but more. with the same cartridge.. vangunsmith