The Founding Fathers knew damn well that colonial rifles were better than British muskets, and even leased warships for the Navy.
Any weapon that a military might possess is a minimum that a civilian could.
Scalia decided the 2nd really said make no law except reasonable ones. He also legalized the Burning of the American Flag as free speech, not my hero.
The AR15 is the Kentucky long rifle of today.
I would exclude chemical, biological and nuclear weapons from the list. But any weapon that is used by the infantry is not prohibited.