I made an AWM50 a while back (never textured it, lol) and it looked very similar to that one (it was for a game so it was low-pol). But anyway, you're missing the knob decals.

It's not all that hard of a texture, unless you are getting specific in shadows, etc. but I doubt that.
You might want to use a true scope effect where the lens uses a refraction to simulate it.