If you want to fix the gun and ammo box textures looking extremely shiny/reflective, there is a simple fix through console.

If you don't have console enabled go to your keyboard options > advanced and put the check in enable developer console.

Some other maps have this issue as well. I'm not exactly sure what causes it because I'm not as well-versed in mapmaking as I am with coding things.

Type in console. Your game may lock up for a few seconds while it applies this (because it's essentially changing a graphics settings).

Then it should be all good. You might also be able to fix this by turning HDR off in your advanced video settings but I don't know because I haven't tried it.