I hate to keep reminding people about this, but the only organization that can actually determine whether the Tenko adapter is a machinegun (or not) is a court of law...not the BATFE. The BATFE only provides guidance towards prosecution for the Department of Justice. If the BATFE wanted, they could easily recommend to the DoJ that all semi-automatic firearms are machineguns via the ill-defined "...or can be readily restored to shoot" wording in 26 U.S.C. § 5845(b), which is subject to interpretation. A court determination can be a very expensive determination and potentially jeopardizes more than what was initially litigated.
If you poke the bear, the bear gets mad. I can understand how the BATFE could get irritated with so many submissions for 'accessories' that are clearly intended to skirt the intention of the machinegun and SBR portions of the NFA...not to mention outright adversarial submissions for dildo bumpstocks, etc. The relationship between gun owners and the BATFE is broken.
I am in no way suggesting that bumpstocks, binary/resetting triggers, and braces are bad in principle. However, IMHO, the relentless pursuit of these 'accessories' has created an environment where legitimate accessories for NFA transferable machineguns, such as the Tenko, suffer collateral damage by being scrutinized much greater than before. Sadly, this unintended consequence has the potential to extend to all semi-automatic firearms as well. We all should stop poking the bear and turn our energy towards educating the general public about firearms in a positive way. Perhaps this could even lead to the eventual repeal of the NFA (or portions of it). If some factions keep going hyperbolic against the BATFE, we ALL are likely to lose out in the end. Only 32% of Americans own guns...a smaller percentage of those care about 2nd amendment rights, and only a tiny percent care or even knows about the NFA.
v/r,
Esox