Nobodies advocating machine guns and grenades. We just want piston grips, adjustable stocks, bayonets, flash suppresors and 30 round clips.
Also the founders were smart enough to know arms would get more advanced. They had every intention of saying that the public should have access to the same weapons the armies who invade us might use. So they may even say today we need machine guns. But we will relent and just maintain the status quo.