Often concept art doesn't make it into the games or films they are designed for. Borderlands, while proudly baring its loose and comic book-esque style, still has to dumb-down certain parts of their designs for them to fit into a restrictive game engine. For this reason, I decided to base my prop directly from the concept art which the standard in-game Dahl assault rifle was from. Doing this gave me some artistic freedom too, since the reference pictures I could scavenge were far from all-encompassing and I prefer to tweak my creations according to the things I can recycle.
This project turned out really well and was a thoroughly enjoyable build. In total I spent somewhere in the region of 300 hours on the build, although if I had made fewer mistakes and done certain parts more efficiently, this time could be reduced to under 100 hours. The cost for me was around £120, the main expense being the paint followed by the sight. Bearing in mind I work in such a way so as to favour using things I already have rather than buying new things, someone who has less materials or tools than me could spend well over £250.
I don't expect anyone to read this instructable from beginning to end, but I hope that people interested in prop-making or similar will find some of my methods resourceful.