One of the more powerful weapon options for Killa Kanz in the new codex is the Grotzooka, a huge blunderbuss that fires scrap gathered from the floor of the Mek's workshop. I've played a few games using this weapon and I have to say, it ROCKS!

Since Games Workshop doesn't make a bit for the Grotzooka, I'm forced to take matters into my own hands. I've been wanting to do my own resin casting for a while now and this is just the incentive I need to get started. I'll be making a prototype model based on some concept sketches, and then making a mold from RTV silicon so I can cast duplicates in resin. This will be the first of what I hope will be a series of custom resin pieces.
 

Here's my first sketch for the scrap gun. It's not much, just a flared blunderbuss barrel attached to a box.

It's got top loading magazine and an ejection port on the side.

Not all that great, but it got my creative juices going and paved the way for...

Sketch number two.

This sucker is more beefed up than the first one, and looks more menacing. In the game, it fires two blast templates so I thought the twin barrels would fit nicely.

In the end I decided that the twin ammo drums looked a little too high tech considering this thing is supposed to be firing scrap from the floor of a garage.

Besides, it looks too much like the twin autocannons on a Marine Dreadnought.

On to design number three.

I ditched the idea of an ammo magazine and built a 'hopper' instead. Since this weapon is pretty low tech in it's concept, I figured the Meks would just dump buckets of scrap into to top of the weapon.

While I like the dual barrel design, I'm worried that the muzzle size might be too small on the final model if I kept them both. So...

I cooked up what I think will be my final design. I kept the low-tech ammo hopper and opted for one BIG barrel instead of the two smaller ones.

A couple of smaller barrels, while they may be more accurate and practical for a multi-shot weapon, just don't have the same "s**t your pants" kind of impact as staring down a gun barrel bigger than your head!

Well, with the design pretty much set, it's time to bust out the plasticard.

Here's the initial shot of the prototype, it's still a work in progress.

I think I was able to match the design of the above concept sketch pretty closely.

The next step will be to fill a few gaps with green stuff and fill the 'ammo hopper' with scrap.

Here's a side shot.

The model is made up of two parts. I kept the ammo hopper seperate so that the weapon could be fitted to either side of the Killa Kan.

And here's the ammo hopper filled with scrap.

At this point it's time to start thinking about making the mold.

As you can see by these close up shots, casting in resin does have it's limitations.

No matter how hard you try, there will be small air bubbles that cause small gaps in the final product, usually in highly detailed areas or at the extremities of the piece.

I've talked with several sources, and there's really no way to completely eliminate them. Heck, even Forgeworld has bubbles in their stuff and they've been casting in resin for years.

I've also learned a few things about creating a master model. I'll probably make another version of the ammo hopper at some point, this time without all the bits in it. This will simplify the casting process a bit, but the scraps and such will have to be added after. It's a bit more work, but at least each scrap pile will be unique.

All that will come a bit later. For the moment, there are some Kanz that need their gunz ASAP so...

I'll be patching the small gaps with green stuff so the Kanz can get to krumpin' foolz. :-)

Well, after some tinkering around with different ways of pouring resin into the mold, I've come up with a method to get pretty clean castings.

They're not perfect. There are still a few bubbles and imperfections here and there, but they're way better than before.

I think these babies have moved beyond the testing phase and are now a viable conversion kit.

Here are the components of the kit: the Gun, Mounting Rod, and Ammo Hopper.

Here's the finished product, attached and painted to an Ork Killa Kan.

Update 11/17/2010

At the request of some readers, I've added some pictures of the Skrap Gun mounted on the 'new' plastic Killa Kanz.

Here you see the Skrap Gun mounted directly to the hull of the Killa Kan, in the same way guns were mounted on the old metal models.

Considering I made the Skrap Gun well over a year before the plastic Kanz were released, the size works pretty well. I also find it funny how the 'official' GW Grotzooka design bears a remarkable resemblance to mine :)

Here I've altered one of the new plastic gun arms to mount the Skrap Gun.

I chopped off the gun (in this case I used the Rokkit Launcha arm) and replaced it with the resin Skrap Gun.

I pinned the Skrap gun in place by drilling a hole into the stump of the gun arm and a corresponding hole in the back of the gun and inserting a brass rod to add some strength to the joint. I kept the cables and glued them in place on the resin kit for stability.