So somebody went and designed a magazine that can be created using a 3D printer. Not only did they design such a magazine but they tested it and it worked very well. This demonstrates the futility of a magazine ban. Combining a box with a spring isn’t exactly rocket science, in fact boxes and springs have been used by humanity for centuries.
I still think the best defense against any firearm-related prohibition is to take a page from alcohol prohibition and the prohibition of some drugs. During the era of alcohol prohibition people were still able to get alcohol. From bootleggers to people making bathtub gin there was no way to enforce the prohibition. Even if you wanted to spend a night on the town you had options in the form of speakeasies, which were secret locations where individuals wanting to socialized over drinks could go. The current prohibition on some drugs has proven to be similarly futile. Those wanting to buy verboten drugs can generally do so easily. We must do the same with firearms. By making firearms and related accessories so prevalent we can render any prohibition irrelevant. The prevalent availability of cannabis has not only rendered the prohibition almost entirely meaningless but it has also allowed advocates of cannabis legalization to point to example after example of people using the plant to no ill effect. Advocates of gun rights have done a similar job with firearms. By making firearms so prevalent in society we’ve prevented many individuals from believing prominent gun ownership is dangerous to society. In the case of a prohibition we would have to step up production to ensure firearms become even more widely available.