Larry - this is 2 years later,but I found this post of yours doing a search on 4 lb cannons. I purchased recently a 4 lb. cannon ball that came from the Rev War battle of Assunpink Creek on Jan. 1, 1777. The battle of Assunpink Creek is sometimes refered to as the 2nd Battle of Trenton. It was plucked out of the Assunpink creek bed in 1975 by a 7th grader and I purchased it from his teacher whom he gave it to this year. What I have found out about the Rev War cannon of this caliber is that the 4 lb. cannon that Washington had, had a bore of 3.20 inches. My cannon ball has a diameter of 3.00 inches and a weight of 3lbs, 10.75 ounces. I wonder if any Rev War cannon of this caliber were used in the Civil War?