A suggestion if I may.
The finest finish you can have ever put on a gun, pistol or revolver rifle or shotgun is the Robar NP3. It appears like stainless.
It is actually teflon impregnated electroless nickel. It does not change any dimension of your firearm and will not show wear after years and years of service.
I have it on one of my colt 1911s and I also had my HK P7M13 and both mags finished with it and highly recommend it for any gun.
If you want black then ask them about their RoGuard finish which does the same thing and lasts as well but is black in color.
Hope this helps