Model and textures by me. The high-res gun was used up-close in the menu, the low-res model was used in game.

Full specs
High-res model
3,925 polys / 3 x 1024 textures (diffuse, normal, specular). 2006

Low-res model
1,722 polys / 3 x 512 textures (diffuse, normal, specular). 2006

Since the game uses a complex weapon upgrade system, I had to rig the max scene with a bone system to automatically align the upgrades where they should go in the game engine.
Here is the max file used to export the weapon.