I think 4 or 5 shells of 00 buck with a side saddle of 5 more is plenty for engaging multiple targets.

There are stories of GI’s in ww1 and ww2 using the standard 5 shot Winchester 1897 to take out entire rows of a trench, or to take on multiple enemy soldiers to great effect.

Train on topping off the tube and a standard pump shotgun is one of the most effective and devastating handheld weapons one can procure

Just my opinion