All I did was open the texture in paint.net and bring down the hue saturation on the _D or _D2 texture. There is a tut somewhere, don't have time to put link here at the moment but is shown how to lower the brightness. Not all the guns have a specular map.
Hardware: Dell Precision 490; AMD Radeon HD 7570; 12GB.
FPSC to GameGuru Tools: AutoWelder/SegAutoWelder, Entity+Weapon Welder, FPEtoBAT