In 1938 of '39, a federal court found the 1934 NFA unconstitutional in light of the 2nd amendment. The US Supreme Court reviewed that in US v. Miller, 307 U.S. 174 (1939), and said that finding the 1934 NFA unconstitutional was unsupported by the available evidence, but that it would be unconstitutional to apply the tax to a weapon that "has some reasonable relationship to the preservation or efficiency of a well regulated militia [or] is any part of the ordinary military equipment or that its use could contribute to the common defense."
The federal courts simply refused to follow the binding precedent.
Same with the Presser precedent.
Complete ruling: Unted States v. Miller
Well, then using that logic, the Supreme Court should have struck down the transfer tax on automatic weapons as unconstitutional, since those are "part of the ordinary military equipment."
But Mr. Miller's counsel didn't appear to argue the other side of the case, the weapon in question was a short barreled shotgun not an automatic weapon, and I believe that by the time the Supreme Court heard this case Mr. Miller had met an untimely death.