I have reloaded bismuth for 12 ga. 2 1/2" and 10 ga. 2 7/8" using 2's and 4's.
The 2 1/2" load is 1 oz of #4 at 1150 and is a stone cold killer on ducks out of my cylinder bored McCrirrick hammergun. I thought it would be of limited use on ducks but was totally wrong.
The 10 ga. load (BB,2,4) is 1 1/2 oz around 1200 fps and is capable of killing any waterfowl at any range I care to shoot at.
Factory ammo is quite a bit faster but no more lethal.