Another extremely "grey area" that the ATF has allowed to get completely out of hand, as far as what is legal, and what is not, in regarding what constitutes a SBR, is the whole convoluted mess that surrounds, "pistol braces".
There have been AR-15 "pistols" for well over 2 decades now. The buffer tube was nothing but a round, smooth tube, that did not allow for anything to be attached to it in any way.
That changed when manufacturers started putting commercial and mil spec buffer tubes on them. That any and all of which could easily accept most any AR-15 rifle buttstock manufactured. All you had to do was slip it on, the exact same way you would on any AR-15 rifle that had an identical buffer tube.
But most understood that by doing that, you would automatically be in possession of an illegal short barreled rifle. Then came the, "pistol braces".
These things look all but exactly like a buttstock, and could be utilized in the exact same manner. And serve as a rifle stock. They came with no butt pad, and were split at the bottom. And were wrapped with a Velcro strap.
The idea being you could push the split bottom over your forearm, then with your free hand, somehow wrap the brace and your forearm up with this Velcro strap. And this was considered the "legal way" for these devices to be used.
It's ridiculous, and wouldn't work, unless you were a skinny, light framed woman, or had the skeletal structure of a 7 year old. Most every adult male who owns one of these, (which is around 99% of them), are owned by adult males, that found out there is no way they could use the thing in that manner.
So they simply shouldered the "pistol brace" in the same way they would any other rifle. Then it got really silly. When the ATF caught on to this, they said it was illegal to fire the weapon in that manner. (By shouldering the "pistol brace" itself).
Thereby making you a criminal by way of your shooting posture. I doubt that anyone was actually prosecuted for this, but it does show just how stupid this has all become.
Personally, I believe the ATF has foolishly backed themselves into another corner over all of this silly nonsense. And I think the final outcome is going to be as I mentioned above. They'll simply have no other recourse but to drop the entire SBR classification altogether.
After January 1, 2026 they're no longer going to be getting any additional funding by way of the $200.00 SBR tax. And there is no longer any valid reason, and / or incentive to keep on with this nonsense. Especially if they're not getting a dime for doing any of it.