I am trying to read the entire ruling on the d.c. gun ban. It is 157 pages, but I ran across this in my reading.

We may as well consider at this point (for we will have
to consider eventually) what types of weapons Miller
permits. Read in isolation, Miller’s phrase “part of ordinary
military equipment” could mean that only those
weapons useful in warfare are protected. That would be a
startling reading of the opinion, since it would mean that
the National Firearms Act’s restrictions on machineguns
(not challenged in Miller) might be unconstitutional,
machineguns being useful in warfare in 1939. We think
that Miller’s “ordinary military equipment” language must
be read in tandem with what comes after: “[O]rdinarily
when called for [militia] service [able-bodied] men were
expected to appear bearing arms supplied by themselves
and of the kind in common use at the time.” 307 U. S., at
179. The traditional militia was formed from a pool of
men bringing arms “in common use at the time” for lawful
purposes like self-defense. “In the colonial and revolutionary
war era, [small-arms] weapons used by militiamen
and weapons used in defense of person and home were one
and the same.” State v. Kessler, 289 Ore. 359, 368, 614
P. 2d 94, 98 (1980) (citing G. Neumann, Swords and
Blades of the American Revolution 6–15, 252–254 (1973)).