Wouldn't swear to it but I always heard that the factory spring is 14 lbs. That seems to be supported by the Wolff link above...but Henning's link lists the factory spring(part# 8.3) as 5.59 kg or a bit over 12 lbs. Since I tend not to shoot light loads, I changed mine to a 16 lbs Wolff when I swapped to Henning's guiderod and have not had any problems. For light/er loads it would seem reasonable to lighten up on the spring.