Working on my first AR-15 build. I have a few questions I want to throw out here. 1) How much should a good M16 Bolt Carrier Group cost for 5.56? I am not needing anything super fancy, just a standard mil-spec quality, nothing too expensive. 2) Is the nickel plated or chrome plated ones really any better? 3) Is there any brands to AVOID? - has anyone used West Fork Armory? 4) Does anyone know where to find them in stock online?