If, like me, you play Chaos Space Marines, you may have considered taking a unit or three of havocs, because of the advantage they have over all other heavy weapon team style units: the ability to take autocannons. Unfortunately, our only option for these weapons is through forgeworld, either the Kalibrax pattern autocannons, or the Legion autocannons. I personally don’t like the ammo feed on the Legion autocannons, and while the Kalibrax autocannons look great, it bothers me far more than it probably should that the muzzle brake vents downwards instead of out the sides. I don’t need to give my havocs another reason like muzzle climb to miss more shots than they already do. Luckily, I had several heavy bolters from the Burning of Prospero box set that could be easily converted to autocannons by adding a longer barrel.
The bits I used are actual autocannon barrels from a combination of Astra Militarum heavy weapons teams, a sentinel, and a taurox. The one problem you may run into is the size difference between the heavy weapon team guns and the vehicle guns. All I did to fix this was cut the muzzle brake off the end of the heavy weapon team, cut a length of the gun barrel off, and glue the brake back on. Then, all you do is cut the stuff off the front of the heavy bolter and attach the new barrel.
The size difference of the two autocannon barrels is a bit exaggerated in this picture, they are barely distinguishable apart from the cosmetic differences. The vehicle autocannons look just right in terms of size, the uncropped heavy weapon team barrels are way too long, and look a little silly to be honest. So far I’ve got 8 of these built, and all I had to do was trade some bits for autocannons.