If you are an FFL, and a person buys this Tac 14 "firearm" and fills out the required FFL paperwork for transfer, there are 3 options- Handgun, long gun, Other (for frames and receivers). It is classified as a handgun because of the pistol grip and shorter than long gun barrel.

A long gun is classified as a shotgun or rifle. (Shotgun with a barrel of 18" or more, and a rifle barrel of 16" or more.) Therefore, it is classified as a handgun.

The Tac-14 is created as follows. Start with a shotgun that has NEVER had a stock attached. Add a pistol grip, and the gun is now considered a PGO (Pistol Grip Only). It is NOT a shotgun, as it is not intended to be fired from the shoulder. Next, add a 14-inch barrel so that the overall length is 26.3 inches. The length being greater than 26 inches disqualifies the gun from being an AOW. So, the BATFE declares that you now have a “Non-NFA Firearm.”The Tac-14 is not a shotgun, nor a handgun, but a firearm. It requires no special paperwork other than the 4473, and the buyer must be 21 years old.

Ok, I'll have to eat crow on this one. I did not know about this classification for this type of "firearm". Yes, it is classified as "Other Firearm", and is not a handgun. It specifically reads "other firearms", such as firearms having a pistol grip that expel a shotgun shell (pistol grip firearm) or NFA firearms.

You learn something new every day!