And the First should only cover religions, forms of speech, printing technologies, venues of public assembly, and petitioning grievances that existed before it was "created"?
The argument that the grandparent is making is that the U.S. Supreme Court recently created legal president that only restrictions on firearms that have similar laws that were enforced during the creation of the Second Amendment can be considered constitutional under the Second Amendment. The argument that that means only firearms similar to those available at the time of the passing the Second Amendment sounds largely similar to the thinking.
And be careful about brining the First Amendment into that... the First Amendment as it was understood by its creators was not about your write to say anything you wanted without government response, it was about your right to publish your own newspaper (or broadsheet/advertisement) without the government issuing you a license or collecting a tax (both of which the colonial government did).
The second amendment was ratified in 1791, and just 7 years later (1978) the Alien and Sedition Acts were ratified by congress, in large part other silence critics of the federal government by making it illegal to say "false, scandalous, and malicious" about it (with the exception of about the Vice-President). And it was absolutely used as a political tool, and this was approved of by the Supreme Court at the time.
So I don't think that anyone really wants this horrible president that the modern Supreme Court has yoked us with. Unfortunately, given the election results, it appears we are going to be subject to these horrible ideas for a whole generation.
That's actually a bad solution. Weapons weren't much less brutal then, mostly just less precise. You'd have people accidentally shooting bystanders in armed conflicts.
We already have that: spray-and-prey is common, as are bystanders killed (even those who are just going about their lives in their own homes). But the weapons of the day were single-shot before reloading. In your argument we would only be reducing the number of bystanders reasonably shot.
The repeating air rifle with a 20 round magazine that Lewis and Clark brought on their expedition was invented over a decade before the ratification of the US Bill of Rights. If you're worried about capacity for indiscriminate violence, there were also cannons and grenades.
Not the fully automatic machine presses. The founding fathers had printing presses that had to be hand loaded one page at a time. Clearly, they had no ability to conceive of more advanced technology than that.
