I just checked to be certain, I ordered their 'calibration pack' from Wolff with 18.5#, 20#, 24# springs, ran them all and the 24# is what I found to be the best. I believe the stock spring is the 22#. The mag springs are the Wolff +10%.
BTW - I also tried a Sprinco recoil reducer and it failed miserably, I couldn't get through more than 4 or 5 rounds without a failure. And it didn't seem to do anything even close to reducing recoil or flip. Recoil doesn't bother me but I was curious as I had never used one before so I thought 'what the hell, why not try it on this little gun?' - MISTAKE to the tune of $70.00! In the end, the 24# spring seemed to help much, much more. I really like this gun!