This is a trollkin thumper, the troll's heavy gun. Unlike many other cannons, this thing fires a solid shot with no aoe but high strength and range. Since it is a troll weapon, it also has a slam ability which is nice for knocking down those pesky heavies.
The crew have blue tartans, like Gunnbjorn's, which signify them as "shooty trolls". I gave some of them extra armour plates and switched up the crew a little to differ them from the second gun.
I used an identifier rune on their left shoulder pads for a squad marking. Sadly, the pictures don't show it well.
The spotter had his whelp scraped off (there is still one on the other), not an easy task.
There are still many more trolls to go, until next round!