This is in response to your communication dated January 24, 2014, to the Bureau of Alcohol, tobacco, Firearms and Explosives (ATF). Your e-mail was forwarded to the ATF Firearms technology Branch (FTB), Martinsburg, West Virginia, for reply. In your note, you ask about firing an AR-15 type pistol from the shoulder; specifically, if doing so would cause the pistol to be reclassified as a Short Barreled Rifle (SBR).

For the following reasons, we have determined that firing a pistol from the shoulder would not cause the pistol to be reclassified as an SBR:

FTB classifies weapons based on their physical design characteristics. While the usage/functionality of the weapon does influence the intended design, it is not the sole criteria for determining the classification of a weapon. Generally speaking, we do not classify weapons based on how an individual uses a weapon.

FTB has previously determined (see FTB #99146) that the firing of a weapon from a particular position, such as placing the receiver extention of an AR-15 type pistol on the user’s shoulder, does not change the classification of a weapon. Further, certain firearm accessories such as the SIG stability brace have not been classified by the FTB as shoulder stocks and, therefore, using the brace improperly does not constitute a design change. Using an accessory improperly would not change the classification of a weapon under Federal law. However, the FTB cannot recommend using a weapon (or weapon accessory) in a manner not intended by the manufacturer.