Bullseye shooters often develop their own loads and tune their gun to the load they like the most. Which for the most part means finding a proper recoil spring that allows the gun to cycle reliably. Unfortunately there’s no exact formula that would help calculate the spring rate, one pretty much has to try different springs and find one that works. That’s why Wolff Gunsprings company sells spring calibration packs. That’s why over the course of years I ended up with a pile of springs of unknown rates. And that’s why I decided to do something about it and figure out how to organize it better.

I found 200mm long test tubes on Amazon, they are reasonably inexpensive and some cork stoppers are also included. I spent a few hours testing each spring with my spring tester and labeling them, but the results are pretty good, now I can easily find a spring of a required rate or see which ones I have.