Well.. that just happened. ATF classification ruling that ArmBrace = SBR

[lazyengineer]

I don't understand why so many people could misinterpret the wording in the March 2017 letter which clearly stated this about the particular brace that was accepted: "With respect to stabilizing braces, ATF has concluded that attaching the brace to a handgun as a forearm brace does not "make" a short-barreled rifle because in the configuration as submitted to and approved by the FATD, it is not intended to be and cannot comfortably be fired from the shoulder" (emphasis, mine). My reading is that any brace that can be comfortably fired from the shoulder would not qualify.

You're not wrong - but with 6.5 Grendel it was tidy, as the open policy allowed folks to run very tidy 12" 6.5 Grendel, which is actually a pretty great build. The letters never actually said what people thought they said - but the ATF enforcement practices defacto said that the arm-braces were OK. With a 12" Grendel the handiness and weight are so incredibly light and small, yet it's still a potent game-killer out to 100 and even 200 + yards, and a gong-hitter much farther then that. It's one of the ultimate general purpose rifle configurations I've ever handled. ATF basically said this was A-OK if not in their letters, than in their enforcement practices; and now they are saying, it's not. So it's a bummer to see it go, and passions are going to run high on this topic.

I'm leaning hard to actually just getting a 12" into the system, just to have it. It'll never be more readily easy to do so, than now. That, and unlike machine-guns, one can be be an SBR / not be an SBR simply by adjusting configuration right then and there. And even remove it from the NFA registry via letter, at discretion. So right now, it's basically free to register, with no engraving, and you can continue to use it right now while under review; and if you change your mind later, a simple letter to ATF and it goes off the NFA and is just another lower. Physically by simply just putting a 16" upper on it, and it's now no longer a regulated SBR, regardless of if the SN is in the NFA - it's not an SBR anymore. Meaning you (or your heirs) can readily sell or transfer it, simply by not having the <16" upper on it. Until you switch it back. Kind of tempting, to be honest. With most NFA items, there's the PITA of what happens when it's time to divest or transfer it. With an SBR, it's easy - just take off the upper and sell that separately from the lower.

Though in some forums, this is a spicy topic of passion and wildly varying opinions. All I will say, is beware anyone trying to goad you into violating what is being enforced as federal law. In AR15.com, there is a collective freakout to goad and belittle people to refuse to take the Amnesty, that frankly, I don't really agree with.