Super-accurate measurement of a ball's diameter, in hundredths-of-an-inch, is crucial for determining whether it is an artillery ball or not. Cannonballs absolutely MUST be exactly the correct size to properly fit inside the gunbarrel.
1- If the ball is even slightly too large, it won't fit into the cannon's muzzle.
2- If the ball is even slightly too small, a lot of the cannon's firing-blast escapes around the ball, causing it to not travel as far as it should... which means it will fall short of the target it is aimed at, and therefore the shot is wasted.
Therefore, EVERY actual cannonball was very carefully manufactured -- and then checked by an Artillery Ordnance Inspector -- to be exactly the right size. Balls which were rejected by the Inspector got tossed back into the melting-pot.
Button King, like others here I am not sure whether your find ever was ball-shaped. But there's a way to pursue the issue, if you want to do the effort. Because your lead object is badly battered, you'll need to weigh it on a super-precise Postal Shipping scale, and then do the math to calculate the diameter of a lead perfect sphere which weighs exactly the same as your lead object. When you've calculated that diameter, check to see if there were ever any cannons which used that size of ball at the spot where you dug it.