You may not get the double or triple the range you may think. Research has been done that shows a 16 inch barrel pistol caliber gives approximately 15 percent more energy than a 4 inch barrel with the same round. It does have a longer site radius which should help in accuracy but a longer barrel doesn't make it that much better over a handgunYou ask "what's the use for a Pistol calibre carbine"? Well, it doubles or triples the effective range for a pistol round while also ringing out all the ballistics of say the 9mm or 45acp cartridge. So, if you can accurately shoot your Glock @ 15-25 yards, then it's very easy to match that at 50-75 yards with a carbine. So, for personal defense without the overkill/overpenetration of a rifle round, what could be better?