This was the last of the recoilless springer match rifles, dating from the early 1980s - a sidelever based on
Feinwerkbau's sliding 'sledge' mechanism to isolate recoil from the stock (and therefore from the shooter).
The LG380 went one step further and concealed the whole sliding part of the cylinder inside a shroud,
so the only things that move are invisible to the shooter altogether.
If you look at the muzzle on firing, you can see it retreat a short distance into the shroud, and
upon re-cocking, the muzzle locks forward a few millimetres into place.