If it must pivot (making a semi-gun-looking-shape) to fire, it can usually be sold as a pistol, while those that can fire from the straight-line configuration must be sold as Any Other Weapons (AOW) with a $200 tax stamp to make, and a $5 stamp to transfer.
Very interesting little toys, good if your pencils ever get snippy and you need to put them back in their place.
Kharn