That one is probably a little easier to picture. (It makes sense when you see them in action.) My other cannon shoots flames and is called a Flame Cannon. although instead of leading hymns down at the local Methodist, they shoot lots of tiny cannon balls at a pleasing rate of fire.
Outnumbered and then some, but not yet outgunned, they've brought with them some rather formidable artillery: two sets of Organ Guns, named for their resemblance to the musical instrument. They wait patiently, as Dwarfs often do, for a much larger force of Greenskins to crash upon their ranks. A line of heavily armoured infantry supported by crossbowmen, handgunners and around 50 flamethrowers. My Dwarfs (not Dwarves) are standing their ground.
