ERROR, je me suis trompé, j'aurais du mettre dans ressort/piston
Let's consider spring piston guns first.
The most powerful spring piston airgun that I know of is the JW80 by Whiscombe. It has opposing pistons that come together like clapping hands. Each is powered by a separate mainspring and the rifle is cocked by three strokes on the cocking lever. I don't own a JW80, whose dual pistons are separated by 80mm, but I do have a JW75, which is nearly as powerful. I have seen 32 foot-pounds from my rifle, though 35 are possible with the heaviest pellets. A JW80 should exceed that by a foot-pound or two.
donc 35 + 2 = 37 ENORME
This JW75 is an underlever spring piston air rifle with dual opposed pistons. Separate springs drive them together like the clapping of hands, producing more power than any other spring piston gun, to the author's knowledge.