How much velocity do you really lose out of a short barrel? Is there some kind of formula? And what do you gain in a pistol caliber carbine? A couple hundred fps? 300? 400? If you only gain a few hundred feet per second when you add 13 inches of barrel, how much will you really lose when you subtract an inch or two? Maybe there is no need to worry about velocity loss in short barrel pistols... Anyone have real numbers? Or any knowledge of the subject?