Shot Pattern Spread from Field and Stream Sept 1964. I do not have the original article but assume the shells were Winchester/Western Mark 5 with the polyethylene shot collar introduced in 1961. Modern loads are very likely better.

YARDS.
..........10 152025303540
CHOKE
Full. 9..121621263340 inches

Mod..12.162026323846 inches

Imp Cyl..15.202632384451 inches

Cylinder 19263238445157 inches

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