If you want a clear, professional job to add service or protection to your firearm, I highly suggest
www.apwcogan.com www.bearcoat.com www.robarguns.com .
CeraKote may be available in a dull gray or "battleship grey" color.
Robar's top notch NP3+ helps clean/support the weapon's surfaces but it's not cheap & gunsmith work may take 3/6mo.
Bearcoat.com comes in grey too and they have short shop times for most firearms. The rifles are in use by some sworn LE agencies & SWAT.
Brownells,
www.brownells.com is good for the "kitchen table gunsmith"
.
MidwayUSA.com offers a lot of stuff too.
ClydeFrog