The bolts with J-locks do have an ill fitting, bunched up spring. Which contacts the bolt body. The contact isn't likely very consistant from shot to shot, and pretty much has to have an effect on the harmonics. So, yes, it should have an effect on accuracy. But, whether or not the effect is enough to be noticeable on a field rifle, is certainly debatable.
I've gotten rid of all the J-locks on my rifles, before ever firing a shot. I just can't stand the detestable looks of the damn things and it bothers me knowing how poorly the spring fits. Whether it has really made any difference, I could not say. But I'll continue to get rid of them immediately, on GP, just the way I'm wired.
- DAA