In the interests of continuing the legal education of our customers, clients, and students concerning firearms regulations, please take a moment to read the following policy letter retrieved from the ATF official website concerning the proper use of the SIG SAUER Stabilizing Arm Brace.
For some time now, the use of this device as a shouldered stock has been something of a grey area. Recently however, the ATF has released a policy letter which more clearly defines the use of this device. As you will read in the letter, the Sig Brace was designed as a “stabilizing arm-brace” not a “stock”. It was never marketed, or intended for use as a stock. Pursuant to the exact definition of its intended use, the ATF has clarified that the use of the brace as a shouldered stock is illegal and any persons desiring to use it in this manner must proceed with the requisite ATF paperwork required for a regular stock on a short barreled rifle. The use of the brace for its intended purpose on an AR style pistol remains perfectly legal so long as the device is not shouldered as a stock.