The number of cannons in each artillery unit at each Unit Size setting is supposed to be:
Small - 1
Medium - 2
Large - 3
Ultra - 4
However, in the actual game it is:
Small - 1
Medium - 3
Large - 4
Ultra - 4
According to [url=
https://forums.totalwar.com/discussion/1143/horse-cannon-unit-glitch]this thread[/url] from a decade ago, this bug was introduced in the last update. I find it incredible that it's never been fixed.
It makes the game unplayable - maybe not technically, but in effect - for those that play on Medium or Large Unit size. I don't like playing on Ultra unit size that much, and don't really have the rig for it.
So, sadly, I am giving up on this game, having yet to start a grand campaign with it.