Here's my take on a cheap hellpistol conversion, that looks pretty much like this...
The real thing...
My attempt...
Step 1: What you need
Catachan Lascarbine
Vox unit backpack
Small piece of plastic tubing (or solid rod)
Pin vice
Superglue
Cabling
Step 2: Cut the lascarbine in the way shown
Step 3: Drill the point where the cables will attach to the carbine with the pin vice
Step 4: Glue the parts of the lascarbine together again and glue the piece of plastic tubing to the back to create the hellpistol shape...
Step 5: Cut down parts of the vox unit to more closely resemble a stormtrooper backpack (you could probably do a lot more with this - I just chopped down the aerial)
Drill the backpack...
Step 6: Put the whole thing together... Job Done!
Again, feedback welcome
Cheers Laney