Bigdog2, The reason I said what I did was from my experience in my fathers gun shop. He built well over 100 of the wildcat cartridge .243 Super Rockchucker. It is a 30-06 case necked down to .243 and the shoulder sharpened to 33 degrees. He built these rifles over the period of 45 years and had several of his early customers come back for re-barreling. There were two customers that stood out: One used IMR 7828 and the other used H-450. The customer that used the large-kernel extruded IMR 7828 did not enjoy nearly the barrel life that the customer that used the spherical, H-450. Both barrels were of the same manufacturer, twist, length, chambering and composition. This, in and of itself, didn't prove anything but this trend was predictable throughout his 45 year career with this cartridge.
Obviously if you have an extreme, low-pressure load using large-kernel, extruded powder and compare it to a scorching, high-pressure load using spherical powder the outcome would be different. I do think that if you use the same barrels, with the same bullets and the same pressure, you will see more throat erosion with the large-kernel powders.