Still not happy with artillery

[Marquis of Roland]

However, afterward the rebels got organized and at least did mount what appeared to be real unified infantry assault. As they approached, I went to switch my flanking lighthorse 6 pounders to canister. Since I did this just before the approaching rebels were in canister range, I turned the fire at will button off thinking that I would turn it back on when the enemy got into effective range.

When you unlimber you have to immediately click off fire-at-will and always direct artillery fire yourself, otherwise random bad things like canister coming out sideways will happen.

Ceasing fire requires you to click both "halt" and then limber within 1 sec.