Spring Tuning

[truck driver]

Been playing with spring length and wire size trying to get the most out of my spring powered D48.
I have found a spring that is shorter but spaced with guide power spacers seem to raise the velocity compared to one that isn't spaced and has more coils.
Can anyone explain why a spring that is shorter and spaced gives more velocity?

[WhatUPSbox?]

If you play with the online spring stiffness calculators (https://www.engineersedge.com/calculators/comp_spring_k_pop.htm), using your spring details, the spring with fewer coils should be stiffer. So assuming the preload is comparable, then cocking it should take and store more energy.

[truck driver]

Thanks for the link.