At typical HD ranges, the shells could hold breath mints and they'd still be quite lethal. But, that's probably not the best choice.
Since you will want to keep your logistics kinda simple, try some light trap loads with 7 1/2 shot. At HD ranges, it'll hit like a solid projectile and not go through 12 walls etc.
However, I'd find a buckshot load that the gun likes also, just in case you need to shoot outside the house for some reason riots, insurrections, block parties gone bad(G)...
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