I refer to the last gun ban (so called 'assault-weapons ban') as the 'Hollywood ban'. It largely banned anything that looked scary in movies.
One video demonstration (by a police office, no less) demonstrated removing the receiver assembly of a hunting rifle, putting it in an aftermarket stock, and it magically became a banned assault weapon.
Shortly after it was passed, I recall a gun show basically attaching parts to a broom (folding stock, large magazine, etc.) and, by the definition of the ban, claimed it would be considered an assault weapon.
According to Wikipedia, it covered:
Semi-automatic rifles able to accept detachable magazines and two or more of the following:
* Folding stock
* Conspicuous pistol grip
* Bayonet mount
* Flash suppressor, or threaded barrel designed to accommodate one
* Grenade launcher (more precisely, a muzzle device which enables the launching or firing of rifle grenades)
Semi-automatic pistols with detachable magazines and two or more of the following:
* Magazine that attaches outside the pistol grip
* Threaded barrel to attach barrel extender, flash suppressor, handgrip, or silencer
* Barrel shroud that can be used as a hand-hold
* Unloaded weight of 50 oz (1.4 kg) or more
* A semi-automatic version of an automatic firearm
Semi-automatic shotguns with two or more of the following:
* Folding or telescoping stock
* Pistol grip
* Fixed capacity of more than 5 rounds
* Detachable magazine
As you can see, items such as flash suppressors have no impact on the threat posed by a firearm, but they look 'cool' or 'scary', so they become a component. And a bayonet mount? Really, how many bayonetings did such a law prevent?
I seem to recall a report presented by the ATF that essentially stated that the ban had no statistically significant effect of crime, but can't seem to locate this.
Rather than understand the analysis and conclude that this type of law is useless for preventing crimes, I expect Obama and the anti groups to instead conclude that it simply wasn't harsh enough and more limitations should be put in place.