its really hard to say exactly what kind of velocity increase you would get with a pistol cartridge in a rifle or carbine barrel. there are a few variables to consider one especially, the type of powder different powders reach their pressure spike ( maximum pressure)at different points in the barrel usually pistol cartridges use fast burning powders which would give a premature pressure spike in a rifle length barrel which you actually could get a lower velocity in a rifle barrel then you would with a pistol barrel say 6 inches in lengthmost likely you wont get much velocity increase if any, do tobarrel drag this is common with 38 special, 9mm, 40S&W,44 special, 45 LCand 45 acp. With factorymagnum loadings i wouldnt expect more then maybe a 200 to 300 fps velocity increases, if you handload and can select the powders used in your cartridge this will give you a better edge over what kind of velocity increase you will get. good luck