223 and 5.56 (nearly identical) are not exceptionally damaging rounds and the AR platform can be configured for 308, 6.5CM and even 300 win mag. Compared to a 300 win mag, a 223 is a bb gun. 300 win mag has around 3x as much energy at point blank but over distances is where it really shines. A person may be able to kill an elk with a 223, with a perfect shot at 50 yards, but penetration is the challenge. Meanwhile, 300 win mags regularly drop elk in their tracks at 500 yds plus. There are also handgun rounds that cause more damage at school shooting range than the 223.
The 223 is also a very popular varmint round in hunting circles, primarily due to the availability of brass and bullets due to military surplus. But there are other rounds such as the 22-250 that push the same bullet at velocities of 4000 FPS, AKA more damaging.
The article also mentions the rising popularity of the AR platform but fails to identify the primary reason, the sunset (not repeal as Chris seems to think) of the assault weapon ban of 1994. While having almost zero effect on firearm homicides, it created a huge market for AR-15s. So the challenge for legislators is to not only create effective legislation that achieves its desired effects without ultimately exacerbating the original problem it was meant to solve.
Stat I saw was that there are 20M AR style weapons out there, only a handful of them are used in criminal activity. There are also millions of lawful gun owners out there and only a handful of gun owners will commit a crime with them.
I am pessimistic that legislation can actually solve this problem, especially since the people crafting such legislation are ignorant of the subject matter.
Where I think there is room would be:.
1. Raise the age from 18 to 25, Ramos bought 2 ARs on his 18th birthday and killed a few days later.
2. Eliminate high capacity magazines. Might save a few kids.
3. Tax and register military style SA rifles. Taxation will make them more expensive and registration will allow LEO to profile and monitor potential domestic terrorists who often show warning signs on social media. This last one could certainly be abused.