Is an ak-74u a sub-machine gun?

Answer 1

Yes or no, depending on the source. Some sources only consider weapons a submachinegun if they fire a pistol cartridge, and others may not. This question doesn't exist with the AKS-74U alone - Heckler & Koch classify the HK53 as a submachinegun, as well, whereas manufacturers of other comparable weapons (say, for example, the La France M16K) consider their products to be rifles. But such weapons do fulfill roles of submachineguns, so it's very plausible to consider them such.