Picked up a 522 3 weeks ago and about 1 in 20 rounds will not fire. It happens with all ammo types and when it happens there is not a firing pin mark on the primer, where as when the round does fire there is a deep circle on the primer. I have examined the FP/Bolt extensively, and can't find any issues. I also swapped a brand new bolt assembly from another rifle into mine, with no noticeable difference in frequency of FTF. Anyone else have a problem like this and find a solution?