This uses the "soft recoil" principle, as seen in the clip the barrel is basically launched forward before firing, thus reducing the felt recoil and allowing it to fire full power ammunition from a light chassis.

In a soft-recoil system, the spring (or air cylinder) that returns the barrel to the forward position starts out in a nearly fully compressed position, then the gun's barrel is released free to fly forward in the moment before firing; the charge is then ignited just as the barrel reaches the fully forward position. Since the barrel is still moving forward when the charge is ignited, about half of the recoil impulse is applied to stopping the forward motion of the barrel, while the other half is, as in the usual system, taken up in recompressing the spring. A latch then catches the barrel and holds it in the starting position. This roughly halves the energy that the spring needs to absorb, and also roughly halves the peak force conveyed to the mount, as compared to the usual system. However, the need to reliably achieve ignition at a single precise instant is a major practical difficulty with this system; and unlike the usual hydro-pneumatic system, soft-recoil systems do not easily deal with hangfires or misfires. One of the early guns to use this system was the [French 65 mm mle.1906](https://en.wikipedia.org/wiki/Canon_de_65_M_(montagne)_modele_1906); it was also used by the World War II British PIAT man-portable anti-tank weapon.