I agree with stomp442. In my experience there is not an interaction between CBI barrels and Sierra bullets. The effect is Sierra bullets; most match-grade barrels, regardless of manufacturer for which I have developed a load, prefer Sierra bullets. Naturally the ability to discern bullet effect diminishes with decreasing barrel quality. That is to say that bullet type effect interacts with barrel quality. So, your observations may be the result of CBI barrels being the only barrel that you have loaded for that is capable of discerning the effect of bullet manufacturer. What is your experience with this observed bullet effect with other barrels?