It wasn't used for assault? That is, assault in the military sense. We have separate classes of weapons for civilian and military assault, I think that's the source of semantic disagreement.
In general, excluding shotguns, all modern firearms have rifled barrels, that is, barrels that impart a spin to the projectile. Rifles have relatively long barrels, carbines have shorter barrels but can be braced on the shoulder, and pistols are held in the hand. I would argue that when a stock is attached to a pistol, that makes it a carbine, a short-barrel shouldered weapon like the US M-4 carbine which has a 14.5" barrel length. The C96 Mauser pistol had a barrel length of 5.5 inches. The M-4 has selective fire, the C96 was semi-auto. The assassins of the Russian royal family in 1918 claimed to have used C96 Mausers. That' all from Wiki.

Wiki says the "Red 9" Mausers were 9X19 Luger caliber, but it makes more sense that they were 9X25 Mauser caliber. The original Mauser round was a 7.63X25mm.