I would not blame the gun for that I have seen it happen on other guns using the same type of bolt/striker as the Blackdiamond. Most of the time it was either too much oil or too thick of an oil. The oil mixes with the fouling and becomes mud. You pull the bolt and clean it and your back in service. Check your trigger group and make sure the sear and release are all cleaned of this goop before you go out next time.

Also try some of the Hornaday 265g flatpoint .429 bullets. They shoot great with most sabots including the green Knights and the T/C Magexpress.