Don't say we didn't warn you, but the ATF on Friday issued an open letter saying shouldering the SB-15 SigTac Pistol Stabilizing Brace "redesigns" an AR pistol (or any pistol, for that matter) into a short-barreled rifle.

The pistol stabilizing brace was neither “designed” nor approved to be used as a shoulder stock,and therefore use as a shoulder stock constitutes a “redesign” of the device because a possessorhas changed the very function of the item. Any individual letters stating otherwise are contraryto the plain language of the NFA, misapply Federal law, and are hereby revoked.Any person who intends to use a handgun stabilizing brace as a shoulder stock on a pistol(having a rifled barrel under 16 inches in length or a smooth bore firearm with a barrel under 18 inches in length) must first file an ATF Form 1 and pay the applicable tax because the resultingfirearm will be subject to all provisions of the NFA.

As you know, we've written about this before -- and some readers said this was a tempest in a teapot. The big question for retailers is whether this ruling bursts the AR-pistol bubble that expanded dramatically after the March 2014 ATF letter saying shouldering the brace did not make a pistol an SBR.

We'll be out at SHOT next week asking retailers and manufacturers what they think this means for them. And keep an eye out for possible arrests. Legal experts say the only way the ATF is going to be challenged on this is in court.

Be sure to read our full story at Grand View Outdoors.