For the metal parts on the gun I like using a bake on paint insted of krylon that comes off with hand sweat.
I did a Polish Tantal with VTH engine enamel black satin & baked it at 200deg. for 30 min. This coating is so tuff I scrubed it with acetone & it didn't budge. It is chemical resistant & can take up to 550deg. It comes in a lot of colors from flats to glosses & metallic.
VHT Engine Enamel