"Making" a full auto weapon I would imagine
The National Firearms Act of 1934 (NFA) defines a number of categories of regulated firearms. These weapons are collectively known as NFA firearms and include the following:
Machine guns
This legal definition includes any firearm which can fire repeatedly, without manual reloading, "by a single function of the trigger",
[10] which is broader than the common definition.
[11] Both continuous fully automatic fire and "
burst fire" (e.g., firearms with a 3-round burst feature) are considered machine gun features. The weapon's receiver is by itself considered to be a regulated firearm. A non-machine gun that may be converted to fire more than one shot per trigger pull by ordinary mechanical skills is determined to be "readily convertible", and classed as a machine gun, such as a
KG-9 pistol (pre-ban ones are "grandfathered")