Most of the shot shells are meant for small tender varmints like snake or rats so they use small #9 , #10, or #12 shot. It also allows for a higher shot count per load.
That is why I load my own shot shells for my 41 mag Blackhawk. I can get a 160 grain load of #8 shot and that is about 156 count per load. They will put the shot threw 3/4 plywood at 20 feet. Tear a snake into ribbons and a cotton tail a new back door.

;D
I use a BPI 410 shot-stump wad and cut it in half. It looks like an hour glass before I cut it. Then I put a charge of 6.5 gr. of universal clays in with the wad cup over powder , cup towards the shot, 160 gr of #8 shot, and then the other half of the wad as the nose. It sticks out like a bullet and I crimp with my Lee factory crimp die. I light it off with a CCI 300 LP primer. Mild and low re-coil, low noise, and a good pattern out to 30 feet and that is the max for my 6.5 inch Blackhawk, after that they spread out and lose steam quickly.
I have also used a 1 inch long piece of 10 mm paper straw and crimped the end similar to a real shot shell and they work just as good for the over shot nose but I still use one half of the stump wad over the powder. Looks like a mini shot shell with real high brass base. Another thing I am going to try is a plastic cover for my e-cig cartridge, it fits perfect and is a little longer than the shot wad.
