There are a lot of "pistol-caliber carbines" (which are also by definition rifles) that aren't sub-machine guns. For example civilian versions that are semi-au

There are a lot of "pistol-caliber carbines" (which are also by definition rifles) that aren't sub-machine guns. For example civilian versions that are semi-auto only ... and very useful in home defense, since they're more easily aimed thanks to the stock anchoring them on your shoulder (see e.g. dccoolgai's comments, some of his fellows on the firing line were using handguns). Or the WWII M1 Carbine, which not coincidentally was the first weapon system we fielded with exclusively non-corrosive primers. Then there's the new Personal Defense Weapon category, with my favorite (in theory) being the P90. Not intended as a classical SMG, but more for people who's main weapon is not a small arm but say a tank. Short and compact to allow easy bailing out of a burning tank, with ballistics intended to give the bearer the best chance once out in the open.