Home grown SMGs in Perth?

[Flying10uk]

It looks like that the receiver, of the smg on the video, was made just by welding or screwing 2 pieces of 40mm x 40mm x 3mm standard,welded seam, box section steel together. Likewise the grip and magazine well look like standard box section, stock material. Very cleverly thought out by the look of it, making use of readily available materials.