The commercial market is working on 250 and 300 rounders now - and that’s not without a valid commercial application. The Marines are seeking super high capacity drums for their M27 IAR which uses AR magazines.
However, most of those we *want* the idiots who do this sort of thing to buy those drums. The big problem these drums have is that most of them are unreliable as hell and are best used as range toys. Many mass shooters have started out with those and had to abandon the drum or weapon because it jammed. I’ve heard many people refer to them as idiot magnets.