To me, a "carbine" is a rifle (even a longer SBR) with a barrel between 14.5" and 16" or so. If it's a pistol (with less than a 14.5" barrel), it's not a carbine. Not dissin' on pistol-caliber pistols, but it can't be a pistol caliber carbine unless it's a carbine. Just my dos centavos. EDIT: Traditionally, rifles had longer--MUCH longer than 16"--barrels and were quite unwieldy to use in many settings. So, if you think about an old-school rifle with a barrel of 22" to 24", then the term "carbine" being used for versions that were a good bit shorter than that, things start to make more sense. Carbines are rifles, but rifles with shorter (I specify 14.5" to 16", because the M4 is considered a carbine, and it has a 14.5" barrel).