You've gotten good advice already, but I'll still comment. Mine likes the .440 with a thin patch (though it is slightly harder to load this way). The .433 diam ball will also work and may be easier for you to load (though these are harder to find). The gun IS a close range piece anyway, so any slight differences in accuracy are moot anyway.
The ease of loading might be more your "cup of tea". I prefer mine to "shoot harder". I don't go more than a .38 Special empty case full of FFFg black powder--about 22-24gr capacity. I personally would never shoot Pyrodex, Triple 7, or any other substitute.
I have tried the gun out on a bundle of old cereal boxes (wet or dry, your preference) that have been collapsed and tied together. These make excellent tests for penetration and if you have kids, you go through enough cereal to keep a good supply of boxes on hand. FYI, I got about 2 1/2" of penetration in the cereal boxes (wet). It's no powerhouse, but it would work quite well across (or under) a card table!
Shoot Safely,
WV_Hillbilly
PS Don't try to make some kind of "magnum" out of this gun. You're just blowing the extra powder out of the muzzle and wasting it. Also, IF you are fortunate to have one that is suitably accurate, it makes a good hiking companion to deal with "legless vermin" (i.e. snakes). Just remember, PRACTICE!
