R.S. Robinson, and Australian designer made this particular gun. It features a mechanic know as constant recoil. The thought is that if the force applied to the operator is constant they can adjust their weight to control it’s effects, mitigating extreme recoil.

Rest of the article for those who want to read about the man behind it:

If you liked this post there’s another one of his inventions the SR-11 posted on the community.