Also [@Pathfinder], my inner weapons/numbers nut coming out to play, but judging by the picture of the bannerlord, I think your gun is more in line with a +105mm cannon instead of a 60mm cannon. 

Not too certain, as I don't know of many ~60mm cannons- except maybe some WWII tank guns- most 60mm shells tend to fall in the line of mortar style weapons as opposed to cannons, which tend to fall into either less than 40mm (rapid firing autocannons) or more than 100mm (heavy tank cannons)

-shit, sorry for doublepost-