I-We've been shooting canons at black-powder rendezvous since 1973.

In the 70's Taylor (bro) had a 3" field piece - made from heavy wall seamless tubing, with another collar of the same stuff heat shrunk onto the breach. The collar had the trunions. Taylor made the carriage like a normal early civil war carriage with antique wagon wheel set he found on an old farm. The cannon shot 3" cast iron balls from a gold mill. We used 1/4 to 1/3 pound of 'canon' (ICI 1F-extreemly coarse - chunks up to 3/16" long) powder per shot and the balls were supersonic and invisible in flight.

Here's my bro - aligning the removable sights on Hatchet Jack's cannon. The rear ladder sight, pivots on a pin sticking out from the cascabel. the front sight, is silver brazed to a muzzle plug with a bearing in the centre. Both have counter weights to hold them square with the world. It worked a peach.