First, I’d be surprised if even a very high-spec machine is capable of making a single-shot weapon that would work.
Even if that were possible, printing ammunition would be very difficult.
Why would anyone even bother, when you can buy a shotgun for a few dollars in many US states?
Today’s invention is for those who really think that home-printed guns are some kind of serious problem.
Since low-cost ammunition only comes in a very small number of diameters, each printer should contain, as embedded code, a routine which detects the design of a cylinder with one of these dimensions.
This would cause the machine not to accept any such design file for printing…or better yet, create the desired hardware using a slightly smaller diameter, making any kind of ballistic use impossible.