For my beater pump shotgun, the best load I’ve found for it is the Hornady 2.75 inch, Critical Defense, 00 Buckshot load.
Despite being a relatively soft shooting load, it still launches eight 00 pellets (about .33 caliber each) at an advertised 1600 feet per second.
Ten shells come in a standard box. That’s perfect for an extended magazine tube. The ballistic trade-off between 3 inch and 2.75 inch shells means little, compared to magazine capacity, in my estimation.
All ten 2.75 inch Critical Defense shells in the box fit within my Rock Island Armory M5 Pump gun with a 20 inch barrel and the KAK extended magazine tube.
Eight shells load easily into the magazine tube with nothing in the chamber. With three inch shells, magazine capacity drops to only six shells. I’d rather have the extra two 2.75 inch shells than lose two of those for the extra oomph of 3 inch shells, which just adds to an already significant recoil.
An additional two shells fit within the double shell carrier in the stock. Two 3 inch shells won’t fit into that carrier; only one will.
When working alone outdoors, I like to keep this shotgun close by, usually in the truck.
At home, I would never use a long gun with a sling. Slings tend to find and snag door knobs, even when the lights are on.
But for both indoor and outdoor applications, Hornady Critical Defense 00 Buckshot is an excellent ammunition choice for self-defense against everything from bandits to bears.