Trying DIY Havoc Autocannons

After assembling my new box of Finecast Havocs, I find myself drawn into the trap of wanting four of every field-able Havoc weapon. Since GW has not deigned to release a Havoc box yet with the value of the Space Marine Devastators I have the option of buying four boxes of Havocs (ouch) or converting my own. Cheapness ... uh, I mean creativity! won out.

 Here is iteration #1, based on (what else) the heavy bolter that comes with every box of CSM. I would still like to mount an ammo box under it and re-position the ammo feed to look like it's feeding into the cartridge ejection point, more in line with the "official" autocannon.

You can see that they really aren't dramatically different side by side.

I pretty much free-handed the holes in the barrel, which leaves them a little wonky. The square mount at the front is just a section from a chainsword with the sides filed down. If there's one thing I have plenty of it's chainswords.

 Okay, so for the next one, I wanted to try to make the holes more even. To that end I created a fixture of plastic to lay the tube in and mark the holes. I pinned it to increase strength.

The next step was to mark the placement of the holes, based on the original Fincast Havoc.

 To mark the holes I laid the barrel tube into the V of the fixture, then laid a small rod next to it. Getting a straight line would have been hard without that extra spacing. I used an awl to poke holes at the marks.

 After drilling out each of the marks, I can't say I'm entirely happy with the results. It's certainly closer to being in a straight line, but not quite there. I was able to make both barrels look better with a little selective pin-vise work, but of course didn't take a picture. I'm thinking maybe gluing a small square piece to act as straight edge instead of the rod. If I make the square piece 1/2 the diameter of the barrel that would give me a very precise spot to mark. Of course by the time I get this fixture perfected I will be done converting autocannons. I suppose I could use them to make Ork big shootas or something.

I still have two more to go, so more improvements should be made. I plan on trying a pistol arm for the next one that should more closely resemble the official autocannon's grip.