If criminals threw the machine guns in the ditch after a crime like they do their hi points then yeah I guess he'd have access to them too. If every gun in the world disappeared then he'd use a bat, a knife, a stick, or maybe his fist. The gun isn't the problem with the situation.That shows exactly what you know sir.
He hasn't done it because he does not have (nor is likely to acquire) the technical savvy or access to the machining capabilities to perform these operations and create a workable full-auto firearm. If, however, we made machine guns legal and unregulated, he wouldn't have those impediments to deal with.