I use a 15lb recoil spring for 9 major. A 14 lb spring for minor.
I think it depends on the barrel, the comp, the type of slide , and the type of powder you use. The lighter the slide the lighter the spring. The longer the comp the lighter the spring and so forth.
My open Glock is a built on a Glock 17. So my slide is lighter than a Glock 34.
Bottom line is you need to buy many different spring weights and see what works.
Craig