Please read it. I'm 100% right.

     As used in Section 33700, “firearm barrel” means the tube, usually metal and cylindrical, through which a projectile or shot charge is fired. A firearm barrel includes any forging, casting, printing, extrusion, machined body, or similar article that has reached a stage in manufacture where it may readily be completed, assembled, or converted to be used as a firearm barrel, or that is marketed or sold to the public to become or be used as a firearm barrel once completed, assembled, or converted. A firearm barrel may have a rifled or smooth bore.

Put compressed air (or maybe some capped off black powder) in tube, it will expel a projectile. PVC pipes are readily convertible into a tube through which a projectile is fired.

Have you read the bill? It literally outlaws (without background check) any piece of pipe which you can readily fire a projectile from. You can do that with pretty much any pipe, just by adjusting the charge and projectile size/type.

Even the process used to make PVC pipes is explicitly called out, which is extrusion.