Rule Of 17, Again


I tried a search and was not able to find the info. for which I am looking. I’d like direction on information on shot diameter and shot size….I know there is a formula to determine diameter from size?

Thanks, Troy

Dear Troy,

Sure, nothing easier. American shot size (just about every country does it a different way) is based on the “Rule of 17”. Simply subtract the diameter of the pellet in thousands of an inch from 17 to get the size number. Also, subtract the size number from 17 to get the diameter. Example, a #9 pellet measures .08″ (17-9=8). A pellet measuring .11″ is size #6. (17-11=6).

I am terrible at math and even I can do it, though I have to engage my entire collection fingers and toes in the process.

Best regards,

Bruce Buck
The Technoid at <>
(Often in error, never in doubt.)

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