Note the behavior of the device on recoil when held in the hands, without the benefit of a stock to act as a brake against the shoulder.

https://youtu.be/VcnLja_DuwM

And here is one where the breech flies off, due to its low mass, per the designer.

https://youtu.be/MbcMwPdoEd0

Interesting that the amateur job in the first video did not lose its breech even though it does not appear to be of much greater mass.

The blow forward action-

https://youtu.be/YKo06FgXlMM

Interesting to ponder how this phenomenon affects a break open shotgun action.