As a point of interest (or not, depending on your point of view) U.S. Army infantry companies each had two M-1200 Remington 12 gauge shotguns on strength as company weapons. I can’t speak for current TOE but this was common from WWI up to the late seventies. Primarily used for guard duty around installations where a high velocity weapon would be inappropriate, ammo dumps etc. They were also carried in Vietnam by some troops who found them useful for clearing bunkers etc. I however always found this to be something of an affectation; a grenade was a better tool for the type’s fortifications we encountered and an M-16 a much more useful weapon.