You believe that all these guys getting thrown backwards were faking it?
They are not faking it, but that rifle is more or less an experiment in how much a human can take, it's not a commercial venture. It puts out about the same power as a .50BMG but without any muzzle brake, and without the 30-40lb weight of a typical .50BMG rifle.
However, even taking a bullet from a .50BMG won't knock you down.
Here's some photographic proof.