Bolt-ons are done by automobile fanatics or those who are referred to as modders. There is absolutely no standard bolt-on since modders are distinctive from each other. An entire bolt-on to at least one modder is just a partial bolt-on to another. That’s how varied this industry of endeavor is. https://bookmarknap.com/story8194134/not-known-factual-statements-about-lightweight-bolt-carrier-group