This is an interesting discussion. I thought I would jump in here. I have a question, how many and what size projectiles in the 6pdr canister used at 250 yards?

I have used canister in a 12 pdr Iron Napoleon at 120 yards and found that it only spread across an eight man front. Out of the 27 balls we averaged 24 hits on the eight men. The ground was hard and sloped very slightly away from the gun. It was interesting to not on the high speed film the difference in the time of the first hit to the last hit, as the balls that bounced off the ground arrived later than the ones that didn't.

At Grayling we fired on the 300 meter range and it appeared to be about a 75 foot spread, difficult to tell for sure. I would note that there was still enough energy to cause some of the balls to break upon hit a concrete wall. At longer ranges it is difficult to determine the spread without a set of targets that spread across the range. I use zinc balls and would recommend that over cast iron as that would produce less wear on the bore.

I have used .65 lead balls in my 10 pdr Parrott. The spread appears to be similar to the 12 pdr, but I don't have definitive proof of that. I would note that the larger balls get a better bounce than the smaller ones that tend to dig in or slide along the surface of the ground.

Benton's book "Ordnance and Gunnery" states that the spread (under favorable conditions) is about one tenth the range.