There must have been preload on the original springs as in the little foldout booklet that came with them originally, it demonstrated placing the rifle muzzle down and compressing the spring into the cylinder using the stock and trigger block section. Edbear who unfortunately seems to have lost access to this forum would be your man for this info, as he did quite a lot of work on spring lengths, but I think you can find him still on the other airgun forum.
There is quite a bit of his info in the technical section of Dannys excellent vintage airgun resources too.
Last edited by silva; 14-01-2023 at 08:15 PM.
"helplessly they stare at his tracks......."