Here's the thing... In 2010 the number of ARs sold in the US was estimated to be about 2.5 million. By now that number is probably about 3.5 to 4 million and rising. And that does not account for AKs or the many other military styled rifles. Out of 12,664 murder victims last year, 323 were killed with rifles. That is ALL rifles of any type and calibre including bolt action. (I haven't been able to find statistics for ARs only). In other words, the chance of being murdered with an "assault" rifle is pretty damn slim.
None of this is to say that we cant restrict the sale of them
, perhaps as a new class of weapon below class 3 but more restricted than standard hunting rifles. (although tighter background checks for all weapons might make this un-necessary) They should probably also be banned from sale by multi-product stores such as Walmart and restricted to sales by certified gun dealers. As anyone with any experience in marketing knows, the more a product is seen by the general public, the more that product sells.
I try to imagine a workable set of rules for ammunition capacity but the best I can come up with is a ten round limit (this is the new average for "low" capacity mags) with 30 round mags classified as Class 3. But that would require a massive retrofit of hundreds of millions of magazines "in the wild" now. And such a move would be completely un-enforceable except retroactively should someone be caught with a banned capacity mag.
The bulk of changes and IMO the most effective still comes down to tighter background checks and tough laws for the storage and availability of weapons, along with greater availability of mental health services for those families who cannot afford them now.
I would also call on the NRA to provide better training and information as a way to avoid much stricter rules and regulations. From my experience taking an "approved" NRA handgun safety class, I believe they can do a lot more to stress safe storage, responsible use, and restriction of access by people who may have mental health issues within a gun owning household (a subject that is not currently covered at all).
But once again, with almost 4 million responsibly owned ARs and probably another million or two other "assault" weapons of various types out there, the guns themselves and the hundreds of millions of hi cap mags are NOT going away. So if you really care about getting something done and making our children and ourselves safer, lets focus on things that will have the most impact such as improved background checks, stricter laws requiring safe storage and availability of weapons to other members of household or thieves, and better availability of mental health services for those in need.