There was a guy in the reloading forum a few years back that did some load development and all he changed was the COAL of his 308 cartridges. It's funny because the end result was best accuracy with a crimp right in the middle of the cannelure. The group sizes were all over the place, so this is certainly a factor when you're loading some rounds. I find with the M305 that it's highly sensitive to the slightest powder charges, more than half a grain in my rifle was the difference between 1.5 inches and 2 inches @ 100 yards.
I don't recall which powder, primer, brass, bullets or gun that he used but it was nice to know that the manufacturers put the cannelure in the right place.