Let me clear up a few fallacies here:
Worlds Spanner:
First, these are not just jazzed up civilian rifles. They are "civilianized" or stripped down military weapons. The basic firing mechanism is the same, it just has the fully automatic mode disabled. This means that it is possible to UNcivilianize them, and such kits can be legally sold.
Complete full auto parts sets are legally sold as replacement parts for those who
legally own the full auto NFA registered guns. To purchase them, you must send the dealer a copy of your NFA tax stamp paperwork.
There are
incomplete (usually missing the bolt carrier and autosear) parts sets being sold because many parts are interchangeable between semiauto and full auto models.
Any semiauto weapon can be converted to full auto by a qualified machinist. Some are just harder to do. One easy (for a machinist) popular pre-86 (legal) conversion was to the Ruger 10/22 rifle, which is hardly a military arm. Do you want to ban .22 rifles as well?
BTW, a Colt AR is one of the hardest rifles to convert to full auto because not only does the bolt carrier have the full auto trip cut out, there's a block of solid metal in the spot where the autosear would go on the military version. The parts simply won't fit in place without a machinist spending several hours hogging out the channel and then drilling the mounting holes.
Even after that's done, you still need the parts set and a bolt carrier from a full auto version.
This isn't something Bubba can do at his kitchen table with a dremel.
Besides, possession of a non-NFA registered machinegun is worth 10 years in prison and has been since 1934.
Second, assault rifles do in fact have a dedicated purpose: mass murder. There are three basic companants that all assault rifles share. First, the high speed firing mechansim (it may only be semi-authomatic but it can fire as fast as you can depress the trigger which is pretty damn fast). Second, a high capacity magazine. These are illegal under the current ban, but old magazines have been grandfathered in and are legally being sold on new weapons. Finally, a pistol grip. This allows you to hold the weapon at your waist and spray fire, as you see in the movies. If you use it hunting, your deer or whatever will end up in pieces. If you use it for home defense, you'll really fuck up your bedroom. But if you use it for crime, you can mow down many people very fast, including cops with body armour and their little pistols.
Edi addressed the pistol grip fallacy.
As far as the 'high speed firing mechanism' bit goes, that's a trait shared by
all semiauto rifles, including my Grandfather's Remington Model 4 and the abovementioned Ruger 10/22. It's disingenuous to claim that a semiautomatic action is a feature of an 'assault rifle' when all semiauto rifles possess it.
So-called 'high capacity magazines' (I prefer to call them 'full capacity magazines') aren't an issue in 99.9%+ of all criminal misuse of firearms.
The DC sniper case is an excellent example. They used a Bushmaster semiauto 'black rifle', but they might just as well used a single shot because they never fired more than one or two shots, much less all 30 rounds from the rifle.
And even in the few cases where they may be an issue, how long does it take to change a magazine on a firearm that uses detachable box magazines?
Not very long.
E.G. When the Bushmaster used by the DC snipers was stolen from the factory by an employee, Bushmaaster just shrugged and wrote it off, never investigated or anything. And that rifle sells for over a thousand dollars. Fucking criminal.
Incorrect. The weapon was stolen from a gunshop in Washington state (Bulls-Eye Shooters Supply, IIRC). Bushmaster had nothing to do with the theft of the rifle.