The short shotgun is okay under the following rules. It can be as short as you want if: It is a "factory" barrel (not cut or altered by a gunsmith) The stock does not fold or telescope, and the shotgun is not a semi auto.
For rifles you can have them as long as they are over 26" in length when telescoped or folded. If they are less than that they are restricted and can only be taken to a
gun range. These have to have factory barrels as well.
You can "saw off" any barrel as long as the barrel is 18.5" or longer when you are done.
There's no extra tax on short
guns here - although buying an aftermarket short barrel is often quite expensive anyway.