From AD Arms Website

"This mainspring came about at the request of customers simply wishing to be able to get a spare spring for their rifles without having to deal with Ruger.

This spring is approximately 2-3lb lighter than the factory spring which measures at just about 32lb.  This spring will "potentially" get you easier cocking and testing has shown no changes in accuracy or reliability. 

However the test pool has been limited to only a handful of rifles and just as with changing any other part of the fire control system caution should be a priority until reliability is tested and confirmed. If issue should arise you can always reinstall your factory spring.

Although I have tried this spring in several variations of Ruger rifles it has not been tested in all of them, so fitment may be a problem in some variants. Please contact AD Arms for questions about fitment."