I've had really good results using the Barnes TSX line in a few different rifles, including 270. The TSX design seems to have solved some of the erratic behaviour from the original Barnes Bullets, and they do seem to be quite accurate in most rifles.
I also like Ballistic Tips, and more so the AccuBond / InterBond type of bullets. The Ballistic Tips open up quite rapidly and are probably not the best choice for your 300, at least in my opinion. I'm sold on the TSXs now though. You can order a free DVD from the Barnes web site on the TSX bullets. It's more of an info-mercial for their own product, but it's kind of cool to watch, plus it's free.
www.barnesbullets.com/