First of all, all credit for this should go to _Toast_ who came up with the idea.....I've just permanently borrowed the idea....

Ok, to make an assault lasgun, you'll need a lasgun and boltgun, a sharp knife and some glue.
Heres a lasgun and bolter I prepared earlier:

(Any type of bolter will do, just as long as it has a magazine clip and not loose bolt rounds)

Next, scrape the winged skull off the lasgun, and remove the magazine and the bayonet fixture. You'll end up with something like this:


When thats done, cut away a section of the rifle, this is where the grip will be placed later. It should look like this:


With lasgun prepared, move onto the bolter, start off by cutting off the bayonet fixture and dot targeter, then cut off the muzzle (keep this). Cut the clip and the grip from the body of the weapon. These are the three pieces you need;


Now, its just a case of connecting out bitz and creating an assault rifle, or as I like to think of it, a combi las/shotgun;


These are great for Veteran squads or command squads. To create a more high tech look, you can add a scope from the Space Marine sprue or from the Imperial Guard heavy weapon kit.

Enjoy.