I'm have the problem with my Swindlehurst rebarreled to 6BR.....I've taken the bolt apart multiple times, adjusted spring tension polished all mating surfaces, checked the bolt barrel with a light to look for any misplaced chunks of primer cups. Sear on the Jewell trigger is free and not sticking, some over travel on the trigger. Firing pin is protruding .064 from the bolt face. I even replaced the firing pin spring with one 3/4" longer.
At Vokes during the Regional shoot she never missed a beat although I was having some problems previously during my practice sessions. I'm now trying Federal Match GM205M and so far 100% success.
Got to have something that shoots for the Frosty Farky....GO TEAM OKANAGAN.