>There is no effective means by which you could prevent an AR-15 from ending up in peoples' hands.

>a block of metal, a CNC machine

Try not to argue in bad faith as a gun owner challenge (IMPOSSIBLE)

Half of your arguments are "regular men need to defend their houses" and "but black people shoot eachother in the ghetto too". Hint: these are in complete opposition to "Having enough time, money and access to a CNC Machine to make a homemade shitty AR15". Making guns less accessible means less shootings, period.

I'm guessing you need a 4 or 5 axis machine to make a gun. These cost more than the buildings that you need to contain them. (OK, there's this guy, but probably not big enough: https://pocketnc.com/.)

I don't think it's unreasonable to say that if you need to own and know how to operate a CNC mill in order to do a mass shooting, mass shootings are going to decrease. CNC is not "hit print", it's a skill that requires training and development. (Looking at /r/3DPrinting, I can tell you that many people manage to screw that up. CNC is like 3D printing, but about 10x harder. Some may argue that you need some more zeroes on there, actually.)

A golf club is also effective for self defence purposes. In any case, those same tools are available globally and AR15s simply aren't ending up in people's hands, or the hands of school shooters.

Most mass shootings reported in the past few years have been committed with guns that were legally purchased by either the shooter or a family member. Surely illegally manufacturing your own gun (or finding someone willing to illegally do it for you) is a barrier to most would be school shooters.

How many mentally ill school shooters would actually build an AR-15 out of a block of metal? 1%? 0.1%?