A 3” 12 gauge shotgun shell contains 11 balls (.36 caliber/9mm) of triple ought buck.
Five 3” shells in a pump or semi auto shotgun can unlease 55 balls in a blink of the eye and each one of them capable of killing a human at 50 yards.
I read a study years ago about the effectiveness of shotguns for self defence, I believe it was by Peter Capstick. His conclusion was #1 buck was the best performer.
These are for the 2 3/4 inch case.
OOO = 36 cal 68 grain X 8 = 0.81 Sq Inches 544 grains total
00 = 33 cal 53.8 grain X 9 = 0.77 in2 484.2 gr
0 = 32 cal 48.3 grain X 12 = 0.96 in2 579.6 gr
1 = 30 cal 40 grain X 16 = 1.13 in2 640 gr
4 = 24 cal 20.6 grain X 27 = 1.22 in2 556.2 gr
In the 3 inch case the pellet count goes up to 24.