I bought an early one in 1976, a .22 i still have it. It used to eat mainsprings getting through at least one a year. Recoil & vibration was heavy. My dad took it with him when he moved up north 30 years ago & i got it back before he died 3 years ago.
The piston seal had turned to mush & i was lucky enough to pick up an old school maccari tuning kit up off here.
That kit transformed the rifle, no more nerve racking spring compressor jobs, the spring just pushed in by hand with about one inch of preload. Virtually no recoil, less vibration & more accurate. As for the power i had to detune it to get it under 12. You dont need original springs they are a step backwards.