1. As noted here, the Bushmaster rifle used in the Connecticut shootings last week was not banned under the 1994 law.
2. The .223 Remington and related 5.56 mm NATO cartridges are not very powerful. Indeed, many states do not allow either round to be used to hunt deer because they are not considered powerful enough for a humane kill. The .30/06 cartridge used by the Army and Marines in WWI, WWII, and Korea is more than twice as powerful. Even the .45/70 cartridge used by the Army in later part of the 19th century is significantly more powerful.
3. An assault rifle is a rifle which fires an intermediate power cartridge and is capable of fully-automatic fire (i.e., a machine gun). None of the rifles covered by the 1994 ban were assault rifles because they lacked the components necessary for them to function as machine guns.
4. Machine guns have been strictly regulated in the United States under the National Firearms Act since 1934. No new machine guns have been added to the registry of weapons available for non-governmental owners since 1986.
5. Machine guns are not very accurate. Most of the rounds fired miss their intended target. Think about some of the footage you’ve seen of third world fighters blazing away with Kalishnikovs on full auto, usually without aiming. Notice how the muzzles wander around. How many of those bullets were misdirected?
6. I’m about to turn 65. The first rifle the Army issued to me was an M1. By the time I got to Viet Nam, the M16 was standard issue. All the soldiers and Marines who have come along behind me were trained to use either the M16 rifle or its M4 carbine variant. When these men and women are looking to buy a rifle, what do you suppose they are most familiar with? Given that and the fact that the M16 was derived from the earlier AR15 rifle, why do you suppose that AR15-pattern rifles and carbines are popular?
UPDATE—In answer to an email: Yes, I own a Colt AR15 Sporter Carbine, but it’s chambered for the 7.62 x 39 mm Russian cartridge used in the SKS and AK-47 rifles. That cartridge is legal for deer in Maryland.