I use the 15# spring from CZ Custom in my SP01 and my 75B in .40. Recoil is fairly light, and shells normally fall 5-8 ft away. From what I have read, your ejected brass location and the type of ammo you shoot has a lot to do with recoil spring choice. I use S & B 9mm 115g and Blazer Brass 165g in the .40, and both are good for my set up. I was using the factory spring in my 97BD (it's a normal spring!, not like that flat wound thing that comes in the 75's), but swapped it out for a recoil reducer. It definetly tighed up my group at 15 yards.