Questions on bullets and powder

[Harpoon1]

I may be cheating...I would say this is a sub 1/2 inch group (.683 - .264) Do people normally subtract the diameter of the projectile when calculating group size?

Yes, depending on how one measures of course. It?s more accurate to measure from the outer edge to outer edge, then subtract the bullets diameter. Giving a more precise center then center measurement the trying to guesstimate where the center of each hole is.