Perhaps it's just my Libertarian streak, but the whole notion of machine guns not being protected because they are "unusual" and "not typically possessed or used for law-abiding purposes" just rubs me the wrong way. The reason that machine guns are "unusual" and "not typically possessed or used for law-abiding purposes" is because the gov't made sure that civilian ownership of full-auto weapons was "killed in the crib". When the NFA was passed, full-auto was really in its infancy and there were only a few hand-held full auto weapons available with the most common probably being the BAR and Thompson. By imposing a $200 tax on what were already very expensive weapons, the gov't created a de-facto ban since only the very wealthy could afford to legally own a full-auto weapon, particularly at the height of the Great Depression.
Similarly, the Hughes Amendment created a de-facto ban. Because the Hughes Amendment limits the supply of legal machine guns to those already registered before 1986, it drives the prices of that limited supply much higher than what they would otherwise be. While many people could, in theory, own a legal machine gun, the $10K+ prices that most of them have reached due to the Hughes Amendment places them beyond most people's financial reach.
It is ironic almost to the point of comedy that one branch of the government can tell us that we have no right to an "unusual" weapon when the other two branches of the same government conspired to ensure that the weapon was "unusual" to begin with.
Smith, and Wesson, and Me. -H. Callahan
Well waddaya know, one buwwet weft! -E. Fudd
All bad precedents begin as justifiable measures. -J. Caesar