Well, my set up is completly different..... 777 loose powder, and Remington kleen bore primers , in a CVA optima. I have never had a problem and have not heard of this problem, but the first thing I would do is get some new primers and try them. If you are feeling like trying something new, then try the Kleen Bore's ... The work great, and they help reduce the crusty ring left in the bullet seating area in the barrel.
But wheather you change or not, try new primers, or get a new breech plug for it and see if that helps.
MET