And select-fire AR-15s or M4's with short barrels without any law, permit, tax stamp, registration or government interference. Short barrels provide the maneuverability needed in tight spaces. As for the projectile used, AR-15 platforms have many options beyond 5.56mm.
This is from Wikipedia:
In 1977, NATO members signed an agreement to select a second, smaller caliber cartridge to replace the 7.62×51mm NATO cartridge. Of the cartridges tendered, the 5.56×45mm NATO was successful, but not the 55 gr M193 round used by the U.S. at that time. The wounds produced by the M193 round were so devastating that many consider it to be inhumane. Instead, the Belgian 62 gr SS109 round was chosen for standardization. The SS109 used a heavier bullet with a steel core and had a lower muzzle velocity for better long-range performance, specifically to meet a requirement that the bullet be able to penetrate through one side of a steel helmet at 600 meters. This requirement made the SS109 (M855) round less capable of fragmentation than the M193 and was considered more humane.
I reload both M193s and M855s, as well as a number of other 5.56 loads and for that matter a number of other calibers. The each have their own purpose. And yes, they each have their own high capacity magazines.
WARNING: the following link contains gory images of a M193 wound. http://forums.second-amendment.org/index.php?topic=4520.0
The M193 load is the only one I’ll use in our AR’s and M16.I prefer the original twist rate of the M16 too.If the situation deteriorates to point that you actually have to shoot people,then the inhumanity of the wounds inflicted is NOT a consideration.