Gun Control & RKBA

What actually makes the AR-15 deadly is that it fires a bullet. Robert Kennedy was killed by a .22lr from a revolver. A rifle only serves to give the powder charge a longer time to accelerate the bullet which in general only improves the effective range.

The specific magnitude of damage that a single bullet will cause is primarily determined by its energy. I majored in physics and have a detailed understanding of energy and dynamics. The kinetic energy of an object (E) is given by the formula E = 1/2 m*v*v, (v*v is v squared) where m is the mass and v is velocity.

The muzzle energy of a .223 Rem is 1100 - 1200 ft·lb. Comparing this to an AR-10, 2,550 ft-lb. Compare that also to the basic 9 millie which is 350 - 450 ft·lb. BTW the 9mm is one of two guns used at the deadliest mass shooting at a school, Virginia Tech. The other handgun was a .22.

Modifying an AR in .223 down to a smaller case for less powder would be expensive. Also, many people reload their own ammo by saving the brass and adding new bullets and powder.

The average deer hunting rifle fires with more muzzle energy than an AR-15.

I conclude that making this change will, at best, make the modified AR-15 about as deadly as the weapon used in the deadliest school shooting to date.