It’s official, AR-15 arm braces like the Sigtac Stabilizing Brace are fully legal to use with your AR-15 pistols even if you use them from your shoulder. Resting the buffer tube right on your shoulder has always been legal, although a bit uncomfortable, so Sig came along with their Sigtac brace that strapped onto your arm as seen above. But come on, we all knew it was just a comfy (and now legal!) way to shoot your AR-15 pistol from your shoulder. Check out the full ATF letter here.
Don’t have a Sigtac brace yet? I highly recommend them for any pistol build, check em out online HERE.