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Some have been challenged and the decisions of the challenges have given us "case law". "Case law" defines boundaries of constitutionality of laws (among other things). Case law is occasionally reversed or adjusted by more case law. Roe v. Wade is an example of case law, as is every case citing used in any justification of action before a court.
There is case law defining the limits of regulation of the 2nd amendment and every other amendment. One of the examples of case law applying to the 2nd found in USA v. Miller in 1939 was a limit/distinction used to determine if a specific firearm can be under more regulation than others firearms. In this case the firearm in question was a sawn off shotgun. The court decided a sawn off shotgun could have more regulation than a regular shotgun because sawn off shotguns were not "in common use for lawful purposes". This case law has been referenced in many cases since 1939 establishing even more case law. Without SCOTUS redefining the limitations in some other case, effectively overturning Miller, this will be the standard for additional regulation on specific firearms.
Now ask yourself why Bush said he would reauthorize the 1994 assault weapons ban seemingly against the interests of his of his obligations? Why would a Democratically controlled congress fail to reauthorize the assault weapons ban? There were challenges coming down the pike to the assault weapons ban. The challenges mostly based on their statistical evidence that the weapons affected by the ban were "in common use for lawful purposes". Bush allies believed that most weapons affected by the assault weapons ban could be shown to be "in common use for lawful purposes", so did democrats in Congress and the prospect of the ban being overturned could make future legislation more difficult so they chose not to reauthorize.
The point is that there are damned few new gun control ideas that wouldn't require a very rare SCOTUS case law reversal to save. States otoh have more latitude for regulation. Big gun control wastes money lobbying for constitutionally impossible federal legislation. There is a reason the NRA spends so much time and money in the states...