I've finally built up some specific Wolf Guard models to lead my squads of Grey Hunters and Blood Claws - till now I've been using the power-fist models that came with the sets, but now I have the models I want, combi-meltas included.
There's loads of tutorials out there on how to make combi-weapons, and pretty much each one does it somewhat different - and I'm going to be different too.
I've ended up using the body of the melta-gun as the basis of the weapon instead of simply using the barrel and fuel tank which is where I most differ from the majority of the tutorials out there.
Here you can see the melta-gun in question, and one of the older model bolt-pistols. I've used this older bit partly because I seem to have a load of them in my box, and also because it is a nice size to mount onto the meltagun body and is a bit more bulky than the current model bolt-pistol. I shave the top of the melta-gun body to make sure it is flat (there is a little details on there that is lost) along the green line, and I carefully cut off the magazine etc. from the bottom of the bolt-pistol along the red line, preserving the magazine for use later.
The bolt-pistol body is then glued to the top of the meltagun and the magazine behind it (the first weapon I did is the one at the bottom and I'm not too happy with the position of the mag so I'll probably move it sometime later).
There you go, really simple, quick and effective.