In a reply to an inquiry made by a Law Enforcement Officer, the ATF’s Firearms Technology Branch determined that an AR-15 style pistol fired from the shoulder when equipped with an accessory such as the SIG Sauer SB15 Pistol Stabilizing Brace would not cause the pistol to be reclassified as an SBR. It has been previously determined through FTB # 99146 that placing a receiver extension of an AR-15 style pistol on the user’s shoulder does not change the classification of the weapon. Additionally, certain accessories such as the SB15 Pistol Stability Brace aren’t classified as shoulder stocks, and as such even improper use doesn’t constitute a design change. The FTB does note, however, that they can’t recommend using a weapon or weapon accessory in a manner not intended by the manufacturer.
Although decisions can be reversed at any time, this response is clearly in line with the SB15 Pistol Stabilizing Brace as being “ATF Approved” prior to its sale.
sigsauer.com/SigStore/sb15-pistol-stabilizing-brace-552
