According to state and federal law, something is either a firearm or it isn’t. In California, all a hobbyist has to do is drill a few holes into an aluminum lower, add a few parts, and they have an AR15. We will join a California gun enthusiast to learn how to make a DIY AR15. The cost of parts, tools, and blank lowers= $500. Having a legal AR without a serial number?….Priceless.