If it isn't required to make a firearm to function, and the function it enabled isn't restricted, there's no Constitutional reason to control them at all.
Funny story true story the only barrels that fit that gun are those made by the company with integrated suppressors.... so you're wrong but that's never stopped you before
For perhaps the 10th time now: For those firearms that only function with barrels that are integrated suppressors such as the example I linked you? YES.
There are no such firearms, as any suppressed barrel can be replaced by an non-suppressed barrel. Barrel: essential and integral to the function of a firearm Suppressor: not.
See link already provided one of many examples of an integrally suppressed barreled weapon. Also as another poster has already pointed out : since suppressors are "firearms" by law it is in fact essential to the operation of a firearm: the suppressor. Which is what makes it so perfect: the slimy little **** gibbons and their fudd enablers get hoisted by their own petard
Then there is even less legitimate reason for it to be subjected to restrictions under the national firearms act.
I hope the NFA is overturned, though I doubt it will be. It was, from the outset, designed as an end run around the Constitution that never should have survived judicial review.
The USSC is changing and if Trump gets the chance if RBD retires, there might be a chance the NFA in it's entirety gets tossed out the window. It would be an interesting change in the direction of gun banning, when the liberal anti-gunners wake up and discover they not only failed to ban the AR-15, but the M4 just became legal for private ownership. Talk about liberal heads detonating.
In regards to NFA 1934, it's listed as a firearm type on the Form 4. I don't see how it gets more unequivocal than that.