ok ill tell you (me and him work togethor).
ok open the .dds texture of the gun. (if you dont have a .dds import ill convert it for you) next use a brush tool and paint over the scope with BLACK. just like the background. then save the texture in the same file (i would copy all the files and make a second gun, name it, the new texture, gun2_D2.dds or somthing like that. just dont save over the old one. then edit the copyed FPE file to use the "gun2_D2" texture. and then it should work.
thats how you do the texture part.