Mike,
You mean 3/4" bore, right?
The "wall" of barrels was a pyramid of 6 barrels. Each barrel was about 2' across so the pyramid was about 6' wide at the bottom and 2' wide at the top. The pyramid was about 9' high. Not a small target but still hard to hit at 200 yards.
I sighted by looking down the barrel. My first shot landed short so I put a small wedge under the front of the base. The wedge probably raised the barrel about a 1/4". Then I was dead on target.
The recoil was with the rubber feet on. All of my cannons seemed to have extra recoil today because of the wood platform I was shooting off.
The load was 75 grains of FFg.
I hope you enjoyed hearing the applause for a cannon you built.
Dave