Before you complain, yes I agree, TFB content has been too legal heavy in the past couple of weeks. But this morning when I got the ATF letter I thought it would be beneficial to the community to post it. This letter affirms that it is perfectly legal for a shooter to fire a firearm by resting an arm brace, such as the SIG SB15 stabilization brace, against their shoulder, just as it is legal to rest the rear part of a pistol, such as a AR-15 buffer tube, against the shoulder.  Alex Capps can be seen shooting the SB15 from his shoulder in the above photo (Alex used an SBR lower to ensure we were not inadvertently breaking the law, which in retrospect was unnecessary).

Here is the the full letter …