Putting something other than a properly loaded cartridge into a firearm is asking for two things-one, a dangerous load that can and has killed/maimed the operator or bystanders; two-liablity, if you use modified loads you will be crucified in court for your intentions.
Use factory ammo of appropriate configuration..
Okay, let's cut through the bullspit here-
Any modern repeating shotgun loaded with appropriate factory loaded ammunition (argue all day about bird shot, buckshot, slugs if you want) will be more than adequate for self defense at nominal household ranges.
Ideal characteristic's? We all can probably agree on a few short list points:
-18” or so barrel (the shortest a scattergun can have w/o becoming an NFA item)
-with or w/o butt stock-some say a folder is the best of both worlds....
-with highly visible sights, a luminous bead on the muzzle is good, so are rifle type sights or combat optics-is't your dollar (contrary to hollywood, shotguns must be properly aimed to be effective)
-factory loaded ammo of proper configuration for the tactical environment you expect to operate in.
-obtain professional training to know the above requirements and have documented practice as a positive defense of skill and intention if the worst does indeed happen...
Forget exotic rounds like flechettes, dimes, rock salt(?) or flame etc rounds-a waste of both $ and performance, especially if you again, ever have to use it.
Use what professionals use-your life and that of your family is worth every penny, do not skimp, get quality tools and good training, then practice and train your family to react to single word commands-and never use those commands w/o either a pre-planned training session, or in the face of actual threat. (Do not cry wolf to see what happens-never!)
God Bless and MOLON LABE.