This might help a bit:

TOTAL SPREAD (inches)
From Field and Stream Sept 1964

YARDS
CHOKE 10 15 20 25 30 35 40

Full 9 12 16 21 26 33 40 inches

Modified 12 16 20 26 32 38 46 inches

Improved Cyl 15 20 26 32 38 44 51 inches

Cylinder 19 26 32 38 44 51 57 inches

Now fill in that pattern with the # of pellets in the load irregardless of gauge then calculate the energy retained by the size shot (I already have a headache :rolleyes: )

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