just serviced my ~1921 L
Spring was basically a meteor spring, with about 2" total preload - that is just over an inch to press the end block down to contact, then about 3/4" depth of the threads on the block. The wire is around 3.0mm, with a soft wind (lots of coils for the length), which is important. Shoots nicely, and quite easy to cock, at 7 FP. I have no desire to try to inrease it, as it has a nice soft and fairly quick cycle.
HTH - JB
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.