I have never seen a solid shot cannonball with a square hole in it. Looks like it may be something else but I don't know what. They would make good boat anchors though.
If it's a 32-pounder, its holes must have been done later. but I believe it's a corner piece for gates or walls. It does, however, have the appearance of a 32-pounder.
My shot table shows 6.25 inch diameter and 32.4 lbs for a solid. I agree not a cannon ball. There is a small tolerance for the shells but not as much as you indicated.
I should have said that the square hole would rule out a cannonball and that the square hole was cast into the object. I would have to agree with you that all were cast. Sometimes my tongue gets caught over my eye teeth and I can't see what I'm saying.[]
The ball does fit the criteria of being a cannon ball in outward appearance. Could it have been cast round and solid like a cannon ball and cut afterwards with an acetylene torch. The metal does look like it was melted altered at the square openings surface on the sphere it is shiny new looking on the edges of the opening.Just a thought
Well here I am again with a still different thought. I have an old large still-yard some where out in my barn that was used to weigh beef cattle and heaven knows what else. This could have been a sliding ball weight for something like that. At one time I had a wooden box salesman's sample of a wagon scale setup. It is now somewhere in the Smithsonian, but I think it had ball slides on it also. RED Matthews