The type of law that makes me want to pull my hair out...
Except that I don't have any hair.
Arizona Revised Statutes §13-3101(A). Definitions. In this chapter, unless the context otherwise requires:
3. "Explosive" means any dynamite, nitroglycerine, black powder, or other similar explosive material, including plastic explosives. Explosive does not include ammunition or ammunition components such as primers, percussion caps, smokeless powder, black powder and black powder substitutes used for hand loading purposes.
OK, so explosive means black powder except that it doesn't mean black powder.
4. "Firearm" means any loaded or unloaded handgun, pistol, revolver, rifle, shotgun or other weapon that will expel, is designed to expel or may readily be converted to expel a projectile by the action of an explosive.
And firearm means anything that expels a projectile by action of an "explosive." But (3) tells us that ammunition and smokeless or black powder is not an "explosive." So what is a firearm?