Sizes Shotgun shell

[Royal Gun House]

Sizes Shotgun shell
Larger lead shot comes in three sizes: B, BB, and BBB. Smaller lead shot is available in sizes 7½, 8, and 9, with applications ranging from sporting clays and skeet shooting, to non-waterfowl hunting at progressively shorter distances. The larger bird shot sizes (i.e., 6, 5, 4)are mostly used in turkey and pheasant hunting applications where legal. Older shotguns continue to use lead shot, as firing newer, harder, non-lead shot may damage the shotgun, and firing soft metal substitutes for lead shot may not be economical.
Buckshot
Buckshot is simply lead shot formed to larger diameters. Sizes range in ascending order from size B to Tri-Ball.
Comparison chart
Below is a chart with diameters per pellet and weight for idealized lead spheres.
Size Type Weight Diameter
#TriBall(12 Ga.) Buck 20.41 g (315 gr.) 15.24 mm (0.60")
#0000 Buck 5.51 g (85 gr.) 9.40 mm (0.380")
#000 Buck 4.54 g (70 gr.) 9.14 mm (0.360")
#00 Buck 3.49 g (53.8 gr.) 8.38 mm (0.330")
#0 Buck 3.18 g (49 gr.) 8.13 mm (0.320")
#1 Buck 2.62 g (40.5 gr.) 7.62 mm (0.300")
#2 Buck 1.91 g (29.4 gr.) 6.86 mm (0.270")
#3 Buck 1.52 g (23.4 gr.) 6.35 mm (0.250")
#4 Buck 1.34 g (20.7 gr.) 6.09 mm (0.240")
#FF Buck 1.18 g (18.2 gr.) 5.84 mm (0.230")
#F (TTT) Buck 1.05 g (16.2 gr.) 5.59 mm (0.220")
#TT Buck 0.98 g (15.1 gr.) 5.33 mm (0.210")
#T Buck 0.89 g (13.7 gr.) 5.08 mm (0.200")
#BBB 0.66 g (10.2 gr.) 4.82 mm (0.190")
#BB 0.57 g (8.8 gr.) 4.57 mm (0.180")
#B 0.48 g (7.4 gr.) 4.32 mm (0.170")
2 3.76 mm (0.148")
4 3.28 mm (0.129")
5 3.05 mm (0.120")
6 2.77 mm (0.109")
7.5 2.39 mm (0.094")
8 2.26 mm (0.089")
8.5 2.16 mm (0.085")
9 2.01 mm (0.079")
12 1.3 mm (0.05")