There was also some exceptions to the timeline that entered the registry that otherwise would seem out of place. Among them are those which were added during NFA amnesties before the Supreme Court ruled them unConstitutional because they required self incrimination.
The 1934 bill was a ban. It was intended to be a ban. At the time Congress and the courts did not believe they had the Constitutional authority to ban such things. So to ban without outright banning they would impose tax requirements that most would not understand or be aware of, and which would be too burdensome for most citizens. While still having exemptions and work arounds so they could still be acquired by government.
They banned some other things the same way around that time period.
However over time people learned the laws, books were written and people could learn how to obtain such things from a library. The once prohibitive $200 tax imposed during the Great Depression became affordable due to inflation. So by the 1970s it was less of an outright ban.
It was felt it would be overturned at the time of passage by most legal experts, including many that agreed with the restrictions but didn't feel they would pass Constitutional review when they finaly were reviewed by the Supreme Court. The Miller case around that time period even demonstrating this, and all but saying machineguns and other militia suitable arms would be Constituionally protected, however without evidence presented they couldn't determine that a sawn-off shotgun was a militia suitable arm. Nobody showed up to fight the Miller case, Miller was dead, and legal representation simply abandoned the case, and the court couldn't consider what was not submitted for evidence (like short barreled shotguns used in WW1.) But it strongly implied had it been a machinegun and not a sawn-off the case would have decided in favor of Miller.
However the restrictions would remain in place so long before review that over time it gained defacto legitimacy.
By the time of Heller it had been in place so many decades that it was normal.
Even within the requirements of the NFA, originally intended to be a ban, as it became less of an outright ban over time they would tighten the restrictions.
Imports were banned in 1968. Domestic manufacture and conversions were banned in 1986.
NormB said:
And they weren't banned. You just couldn't make another machinegun without a SOT tax as an FFL.
They are banned, by that definition they are not banned in most of the world. Most nations have some means for some to have such things, even though the majority of the citizens may not.
Almost nothing is ever completely outlawed for all elements of society.
The existing purpose of that procedure is to enable the government to still have a means of procurring modern selective fire weapons (like most combat firearms since WW2), since most products come from civilan markets and businesses it requires allowing some regular peasants in that loop to possess them so they can get to government.
Even then to help insure they are still made primarily for government there is things like a demo letter and similar formalities to insure there is actually demand or interest or need from some government agency prior to the peasant just making something.
That some citizens must still have such weapons is from government perspective an undesirable but necessary evil.
Almost all products come from private civilian business, even those that government need. So they have to have a method for some to have such things so government can obtain them.
Everything can be possessed by some people with the right licenses, even the most restricted or outlawed drugs for example have some exemptions or licenses. Yet we would acknowledge that they are in fact banned. Likewise some people had exemptions or met narrow license requirements during prohibition to possess alcohol. Yet it was banned.
So is nothing really banned?
No, it is banned. The litmus test if something is banned is not whether some can still manage to acquire something.
Clearly the formalities demonstrate they don't even want SOTs to freely have the ability to manufacture such things, which is why there is things like the demo letters. They really only want things that there is a strong likelihood are in demand or will actually be going to government. Some merely get around that governmental desire.