Had it pointed out on another forum the mechanical inadequacies of the design of the mount for the autocannon. Usually its just a case of "because
40k" but I came up with a quick fix I hope you like.
I suppose you could call it a hydraulic lock, opposite to the direction of the recoil. I imagine the barrel assembly slides backwards within the body of the weapon like a howitzer. and it has a slow rate of fire.
Also added more mechanicus bling, and tiny rivets.