I work in the plastics industry. There are some grades of plastic that are electroplatable but the majority are not. I'm not aware of any polymer gun components that are molded in the platable grades of plastic. Most gun components are molded in nylon based polymers. PVD or physical vapor disposition is another means to plate plastics but there are limited materials for that process as well. There are more materials that can have a vacuum metalize process on them. Most people don't realize that there are currrently over 80,000 commercially available grades of plastic.