Not sure where this was filmed. Illegal in Canada and the USA, seems to me.
Saw this last spring - someone sent it to me. I've seen - here, I think(12 bore from hell), that a brass 12 bore shotshell base can be put(soft soldered/cemented or glued) on a .50 BMG to make 3 1/2" 12 bore cases, by expanding the case and trimming to length.