Quick Question

I just bouhgt a bushnell radar gun today and was outside throwing of my homemade mound but the thing is i made a dumb mistake the other day and left my bucket of balls on the porch and there was a huge rainstorm so they were all ruined :frowning: :frowning: anyways since i dint have rreal balls i was throwing tennis balls and i got 68 mph about 8 times in a row does anyone know what the speed diffrence between the two balls would be?

4-5 mph

id say it was a bit more

7-8