We shouldn’t get all wrapped around the axle of the term “common.”
We now have a “Miller Test” with respect to firearms and the Second Amendment. The test goes like this: “Does said firearm have some reasonable relationship to the preservation or efficiency of a well regulated militia?”
If the answer is “Yes,” then the weapon is encompassed by the Second Amendment.
So that means that M-16s are covered, short-barrel shotguns (”breaching guns,” “combat shotguns”) are covered, 20mm anti-tank rifles are covered, etc.
What’s doesn’t have such a relationship? Perhaps saps, brass knuckles, slungshots... What’s a “dangerous and unusual” weapon? Perhaps chemical, biological, or nuclear arms, JDAMs, or autonomous air-defense guns...
“Shall not be infringed” covered everything.
Period