The second amendment is irrelevant-

[gejohnston]

110. it really doesn't

both sides claim Miller as a victory as their side. One problem was that Miller's council was not there. The only thing your quote says is that there was no evidence shown to the court that such a shotgun had any military value, not a protected weapon. In other words, if it were an unregistered BAR or Thompson SMG, the decision may have been different.

Gun control advocates point out that for over six decades the United States Circuit Courts, with very few exceptions, point to the precedence of the Miller case while rejecting legal challenges to federal firearm regulations.[5]
Gun rights advocates claim this case as a victory because they interpret it to state that ownership of weapons for efficiency or preservation of a well-regulated militia unit of the present day is specifically protected. Furthermore, they frequently point out that short-barreled shotguns have been commonly used in warfare, and the statement made by the judges indicates that they were not made aware of this.[6] Because the defense did not appear, there was arguably no way for the judges to know otherwise. Two of the justices involved in the decision had prior military experience, Justice Black as a Captain in the field artillery during WWI and Justice Frankfurter as a Major in the Army legal service; however, there is no way to know if they were personally aware of the use of shotguns by American troops. During WWI, between 30,000 and 40,000 short-barreled pump-action shotguns were purchased by the US Ordnance Department and saw service in the trenches and for guarding German prisoners

http://en.wikipedia.org/wiki/United_States_v._Miller
So why didn't NFA ban such shotguns and machine guns?

The purpose of the NFA[1] was to regulate what were considered "gangster weapons" such as machine guns and short barreled shotguns.[2] Then U.S. Attorney General Homer S. Cummings recognized that firearms could not be banned outright under the Second Amendment, so he proposed restrictive regulation in the form of an expensive tax and Federal registration.[citation needed] Originally, pistols and revolvers were to be regulated as strictly as machine guns; towards that end, cutting down a rifle or shotgun to circumvent the handgun restrictions by making a concealable weapon was taxed as strictly as a machine gun.

http://en.wikipedia.org/wiki/National_Firearms_Act