Some shoters firmly believe that the reason the .243 Winchester tends to erode barrels more quickly than the 6mm Remington (which could be debated, and no doubt will be) is the .243's more sloping shoulder and short neck. The theory is that the shoulder tends to direct the hot gas into the throat just in front of the neck, speeding up erosion.
One piece of evidence in support of this theory is that Ackley Improving the .243 tends to slow erosion, but you'd have to shoot out a bunch of barrels to come to any firm conclusions.
“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.” John Steinbeck
