In The Admiral: Roaring Currents the Japanese sniper is shown to have multiple guns. When she fires one, she hands it off to a guy next to her, who hands her another gun already loaded.
In the Crown, at the end of the first episode George VI goes hunting. He takes a shot, then gives it to his assistant, who hands him another gun.
Furthermore--was there a name for the person whose job it was to reload guns?
Haven't seen these, but the second sounds very much like a typical bird hunt on the estate of a great house. The hunters are positioned in stands overlooking the field. A line of beaters have walked in, driving the game birds in front of them into the field. As the birds fly across in front of them, the hunters shoot at them with shotguns. Those typically would hold just two shells, but there could be many birds flying all at once; so the hunter would have two guns and an assistant, a loader, to take the fired gun after the two shots and hand over the loaded one, so the hunter could keep his/her eyes on the birds and keep shooting. As the loaders and beaters were from the village or were servants, and the hunters well to do, or even royal, it's a handy scene for a filmmaker who wants to show class distinctions and rank.