Bolt-ons are done by motor vehicle fans or those people who are known as modders. There isn't any normal bolt-on given that modders are various from each other. A complete bolt-on to 1 modder is just a partial bolt-on to a different. That’s how varied this area of endeavor is. https://growthbookmarks.com/story17959502/5-simple-statements-about-bolt-carrier-group-parts-explained