MT,
The SC in Miller clearly stated what individuals comprise the militia:
The signification attributed to the term Militia appears from the debates in the Convention, the history and legislation of Colonies and States, and the writings of approved commentators. These show plainly enough that the Militia comprised all males physically capable of acting in concert for the common defense.
This statement, directly from the text of Miller, leaves no doubt as to the definition of Militia. "the Militia comprised all males physically capable of acting in concert for the common defense". If you can march and shoot a gun, you're Militia if you choose to be.
Secondly, Miller stated the kind of arms these individuals had a right to bear:
And further, that ordinarily when called for service these men were expected to appear bearing arms supplied by themselves and of the kind in common use at the time.
The mistake in Miller is here:
"It is not within judicial notice that a shotgun having a barrel of less than 18 inches in length is any part of the ordinary military equipment or that its use could contribute to the common defense."
The SC said that in 1939.
Approximately 20,000 Winchester Model 97 trench guns were supplied to the U.S. Army in World War I. 1918... surely the SC should have been aware of that. These guns were still in US Army issue at the time of the decision.
Further, the Winchester Model 12 trench and riot guns were again procured with a total of more than 80,000 guns ordered by the U.S. Government by 1945, more than any other combat shotgun of the time.
Ithaca Gun Co. produced a small number of Model 37 trench guns and a larger number of Model 37 riot guns and training guns.
Stevens Arms Co. delivered trench gun, riot gun and training versions of its Model 520-30 and 620A shotguns.
Remington Arms Co. turned out riot and training gun variants of its Model 11 autoloading shotgun, and Savage Arms Co. produced a number of the almost-identical Model 720 riot guns and training guns.
Clearly, in both WW 1 & 2, shotguns were "of the kind in common use at the time" by the military.
Short-barreled shotguns continue in use in the US military to this day.
So Miller was wrong on that point. That's why it is wrongly decided.
And today? All males physically capable of acting in concert for the common defense still comprise the militia and this shotgun is being tested/used in Iraq:
In late 2003, the Army fielded a Lightweight Shotgun System to troops in Afghanistan, responding to an "urgent operational need" from 10th Mountain Division soldiers.
Able bodied males are the militia. Shotguns are in common use by out military.
