I have been told that the local police load a rifled slug first into their pump shotguns (Remington 870s), followed by 2 double ought buckshot shells and next, 2 number 6 shot-shells. If they have to fire the gun, these shells come out in reverse of the way they are loaded. It starts with the 2 shot shells, then 2 buckshots and last, the slug. This is in case the perp is so hopped up on drugs or something, that the bird shot can't stop him, the buckshot should. Then if all else fails, the slug should finish the job.
I load my home defense Mossberg 500 that same way. If it works foe LEOs, it should work for me.