Thst's correct, it's indeed a 42mm cannon and the damage is damn sucky I have to admin but I wanted so bad to use something else than the Eradicator (it's a good gun but I needed change) especially as I was lucky enough to grab a ql200 Inner Circle Strategic Flamer during the neverending ocean of ql200 mission I'm currently crossing.
So I wanted so bad and I cracked and put something with a lot of boomboomtacatac on!!! but I wasn't patient enough to twink to put ql200 imps on and put the flammer, I will

I actually find it fun to throw a big 10k+ FA here and there.
Thanks for the advice, tho, I'll try to see if I can get my hand on one.
Malic