Uh, pretty sure that's a compressed air blast.
There is no barrel flash at all.
Not even a tiny hint of weapon bolt vibration. 556 has very little to no recoil, but that weapon looks WAY too stable to be in mid cycling.
At close range hits there would have been explosive body debris. Don't see it here.
Again, I see nothing but gas.
This whole thing is way too manufactured to not be an engineered FF.
But I guess everyone has analyzed this to hell and back already.