Hey its Chaos - why not?
Draak Mutilator Cannon R30” Str6 AP3 Heavy 2 Rending, Pinning, Jams, Explodes, 15-20 pts depending on carrying unit/vehicle
In reaction to the losses suffered to the Hurricane Bolter fire from Land Raider Crusaders followed by assualts from their passengers, engineers from the Traitor Forgeworld Draak created this as a means of dealing with the heavily armed and armoured Astartes assault units. Unfortunately this weapon is notorious for jamming and catastrophic self-destruction if crews ignore overheating warnings during extremely long bursts of fire (tempting given the unholy destruction these weapons can cause)
On a roll of any 1’s to hit, the weapon system jams and is nearly impossible to fire next turn. Note that any hits that round are resolved as normal. They should skip the next turn of firing the weapon. If they do, thereafter they may proceed as normal if of course the thing doesn't jam again. The crew can however decide to continue firing immediately next turn in the hope of clearing the jam that way, however they then risk a catastrophic explosion. Any rolls of 1’s in this case cause the gun to explode, resolved as a glancing hit on the vehicle. If carried by a infantry model, resolve as an armour save instead. Any non-1 rolls that would have hit add 1 accumulative to the roll on the vehicle damage table and a -1 on a infantry model's armour save. Of course it goes without saying that this counts as a weapon destroyed in addition to any other result.
A prime example of its use is on the Dominator Assault Raider, the Chaos answer to the loyalist Land Raider Crusader, which mounts three Draak Mutilator Cannons; one in each sponson and another hull-mounted. It serves as ideal support for the troops it carries, usually 6 Chaos Terminators armed with assault weapons and often one armed with yet another Draak Multicannon.
Read & discuss, will probably never see the light of day except in friendly games. If it seems a bit similiar to the 4th edition
CSM Kai Gun daemon weapon, guess what
If I were to model this I would basically take an
WHF Empire Helblaster Volley gun minus gun-carriage and fit small Chaos serpent/dragon heads to the ends of the barrels.