I’m developing a FPS game and also a game engine. Today I have modeled this weapon:
Weapon+Mag have as much as 1188 triangles. Rendering time was 00:19.24 on AMD Phenom II X6 @ 2.8 GHz. (19 seconds)
Weapon+Mag have as much as 1188 triangles. Rendering time was 00:19.24 on AMD Phenom II X6 @ 2.8 GHz. (19 seconds)
Pretty good lowpoly 
Only thing that I notice which is not true to the original is the groove above the handguard. This is the groove for the cocking handle and therefore it should be of uniform width.
Since this is an FPS model I would suggest modeling the cocking handle and ejection port as animateable pieces, too.
Looks like a good start, now go for the texturing:)
It would be nice if you can go high poly with this thing.
I added some details, fixed the groove for cocking handle, and painted it. 2375 triangles.
(edit: added wireframe)
I also tried to extrude the weapon out of a cube, to see how it would turn out.
Next I’m going to once again remake the model, with even less polygons, and generate a texture from the first model.
