since the game was developed by New England grouse shooters who are known to ascribed magical powers to the 16 -
and Foster, a grouse hunter known for his 16 guage "little gun" - came up with the idea of cutting the clock in half to give us the modern skeet course -
why wouldn't they have shot the game with it with it?
even though it was eventually classed with the 12 as regulations grew, it was still what a lot of them shot.