Stocks that modify guns to give the gun a faster fire rate have been around for quite some time. All of a sudden now they are an issue because some idiot employed one. You can make them illegal if you wish, but that won't stop folks from using a method to accelerate gun fire should they want to employ one, Max. Did you know you can 3D print one of these stocks? Most avid gun users don't use them except for target practice fun because they make aiming extremely difficult. This is why soldiers in combat switch to burst or single fire settings in many situations - because automatic fire really only serves well as suppressive fire. And to waste ammunition.
The ship has sailed on any type of "gun control" initiatives. Oh sure, you could put a law into effect to confiscate firearms and some folks would comply. Many would not and they'd find ways around the ban. I personally own several guns that cannot be traced to me in any database. This is not because I plan on committing any crime - that would be the last thing I would ever do. But because if someone came knocking at the door to collect firearms, I wouldn't have to surrender those.
Let me say that I would gladly give up all of my guns tomorrow if I knew everyone else was going to do the same. Gladly. But short of some magic wand solution, that will never happen. There are just too many firearms on the streets in this country.
Ricter once asked me why it can work for airports but not the country. I told him that this was obvious. Airports had been "cleaned" of all weapons and then you have a safe area. You'd have to empty the whole country and clean it before you could do the same thing in the country. There are numerous examples of countries with extremely strict gun laws and murders that occur there.
Find the cause of the problem causing folks to shoot people. Don't focus on the gun (or the stock, or the magazine, or whatever). People will just use knives or trucks or whatever if they want to kill.