Recoil Guide Rod Springs / Recoil Calibration Kits by Wolff Gun Springs
 
These kits / springs are for full-size P320 (and 1911) that use a 1911 style guide rod\
 
Each kit contains 1 each of 11, 12, 13, 14,15lb reduced power conventional recoil springs and 3 extra power firing pin springs (for use in 1911 only).
 
Recoil calibration paks are offered to allow the shooter a choice of recoil springs to calibrate the recoil function when the correct spring rating is not known. The shooter starts with the strongest spring in the pak and works down until the desired recoil function and reliability is obtained.
 
I bought one of these kits years ago. It's a great kit to use to determine which spring your pistol is happiest with. Once I know which weight spring works the best I purchase another new one to return to the kit. This way I have a complete kit with all new springs for the next pistol.