Ballistics have been being studied for a mighty long time. No one seems to have discovered the reversal of motion & reported on it. Upon firing a conventional gun the expanding gases from the burning powder are exerting their pressure in all directions. As the projectile moves forward the gun moves backward.
I have fired a 3.5 rocket launcher of Korean vintage. There was a definite reversal of movement with this, "BUT" this is not a conventional firearm. It is a simple launch tube open at both ends, the "Rocket" is propelled by its exiting gases. There is a definite forward pull from the friction of the rocket moving down the tube & a slight reversal as it exits & the blast of gases strike the muzzle bell, put there to protect the firer. This is of course a totally different situation from a gun having a closed breech.
The shot charge is accelerating as it enters the cone & will continue to acceleraate as it passes through it. The gun also will continue to accelerate in the opposite direction. This will not present a situation where the gun would be moved away from the shoulder, to then return with greater force.
