This is original AWP from Counter-Strike: Global Offensive for sniper rifle in TF2 - AWPer Hand. At first i wanted to fix lens of original AWPer Hand b'coz it's don't have reflections of world at all. But after several fails i am just ported AWP itself from CS:GO with all it's textures, Hi-poly model, normal map e.t.c. It's helped to find out what was wrong with lens and why it's not reflecting world properly and even if fix it (with TF2 textures) it's still look ugly.
The problem is in lens texture and AWPer Hand's scope. This scope is edited original CS:GO scope (well... AWPer Hand is edited AWP). Original CS:GO scope useing unique textures for it, then TF2 texture don't have normal map (but have alpha channel). If try to fix original AWPer Hand "light way" - need just use (port) original texture from CS:GO (VTF + VMT settings), but convert from vertical to horizontal (keeping texture position. Do not rotate!) including normal textures. "Hard way" it's direct port of AWP to TF2. Main problem here is Valve ToS and CS:GO SDK. At the same time, TF2 already got nice texture of AWP in it's folder (TAN stock).
Added Dynamic Lens on scope (look last two screenshots).