You will probably never get the "effortless" opening you are looking for with the Sako factory action since the bolt is a relatively small diameter, so the cocking cam has a relatively steep angle, plus Sako firing pin springs are pretty stout. There appears to be some brass sizing issues, not neck diameter, that need to be addressed as was said. You already have your necks on the small side so don't turn them down anymore. You are on the right track for smooth operation by going to a true BR rifle with a custom action (buy a used one). Good luck with your venture.
