I decided to take the original model and push it a bit further. The background isn't quite there yet, and there's a great deal to do in Photoshop yet (markings, smoke and light effects, etc.) but I thought I'd show it at this point to give a clearer picture of the process. The muzzle flashes are just alpha-mapped and self-illuminated textures. I really don't care for particles in 3ds Max at all- I can see why that sort of work is done in post production instead so much of the time.
The gun is a smart gun/MG42/Oerlikon lovechild, yes.