Instead, get some No Excuses Conicals they are 460 grain and .503 diameter. Load them with about 80 grains of FFFg powder. The accuracy out of my Black Diamond XR is fantastic and I have shot seven in a row without a swab. Anything you hit downrange with one of these is over....

I am wondering if that plastic stem off that lock and load sabot is not melting when the fire come up between the pellets your shooting? Before I curse the rifle, I would try some Thompson Center Mag Express sabots with a 240 or 300 grain XTP bullets and see what happens. Also I would get rid of the pellets. I personally shoot good old fashon Goex FFFg gun powder. And I have fowling but no crud ring. I have a bigger clean up job, but so what. I never took this sport up to wear a white suit and shoot at the range. I also have the cheapest cost powder out there. The powder with the fastest ignition rate, excellent accuracy, excellent water resistance compared to the other powders, and all the smoke and stink a man could want.....