I do not expect to ever want or possess any AR15 pistol with or without an arm brace. So I do not have a dog in this fight. But I do have two observations.
1) My Dad taught me almost 60 years ago that if something is against the law doing the same thing a different way is still wrong. Therefore, if an arm brace on an AR15 pistol is a way of having a short barreled rifle by a different name — anyone doing so proceeds at their own risk.
That's going to be the basis of the ATF's case, and I agree with you there. People are shouldering these, for practical purposes as much as anything else. It's too heavy and awkward a device for anyone smaller than Conan to use effectively just holding it out in space, and even he would benefit from shouldering.
2) Although I am not in a position to give a reasoned legal opinion, it would seem to me that if the BATFE is changing its interpretation of a law such that something which was legal is now illegal — that law is a fine example of a law being void for vagueness.
That's going to get interesting, and one thing I would bring up is the Shockwave and Tac 14 firearms.
I would say "shotguns", but in technicality they're not. Not without a stock.
Yet, there are brace devices that people can place on them, that extend from the rear (like an AK or Scorpion, and unlike an AR where there's the buffer tube *a physical part of the gun design*). Those are not being named or included in this, because they're specifying "short barreled
RIFLE". And the Shockwave would be, I suppose, a "short barreled shotgun".
But, the ATF is attempting to define a legally purchased firearm as an NFA item, because of the attached brace.
As of now, there is no ruling preventing the Shockwave from using a brace... why would a Scorpion or Krinkov be different? Simply because it's different ammo? You can't tell me a .223 or 7.62x39 at close range is
more lethal than a 12 gauge with slugs or 00 buckshot.
It's at least an angle I would present, to show how arbitrary and vague this is.