2-P, maybe what happened to Mr. Hammond is something G. T. mentions in his
"Shotguns & Cartridges for Game and Clays":

"If, however, a man is quite confident that he does better with a different size,
he would be well advised to stick to it as long as his confidence lasts.
Confidence in shooting is worth much more than marginal ballistics."

I must point out that he is talking about using LARGER size shot though, :-)

JC

"...it is always advisable to perceive clearly our ignorance."ť Charles Darwin