Method: Ninja Nub, Kuroyasviel
The textures follow the standard filenames: wpn_ak_74 and wpn_ak_74_bump
wpn_ak_74 is obviously the Diffuse
Information below pertains to _bump files.
so.. filename and filename_bump
Open your _bump.
Run the whole _bump through NJOB then load the normal map that was generated. We do this since the _bump is actually a heightmap which can be converted to a normal map.
Green channel holds the Specular.
Put the Specular in the Alpha of the normal map.
This is your finished Normal Map, export as your Normal.
Now for your Exponent.
Make a copy of the Specular, and then run these curves(control+m) on the copy of the Specular
Output Input 7 93 31 147 125 212
Make a new layer and brush the whole layer as 128, 128, 128, then put the Curved Specular into the red channel of THIS newly created layer.
This is your finished exponent, export as your Exponent.
We now have Diffuse, Normal, Exponent, and Specular in the alpha of your Normal Map.