The theory that used to be advanced was that the sharper shoulder on the AI round protected the throat from erosion. The contention was, if lines extended at the angle of the shoulder converged ahead of the neck of the cartridge, erosion would be increased. This was always given as the explanation of why the 243 Winchester was so hard on throats.
This is one of those theories which, on the surface, almost makes sense but I know of no serious studies done to try and prove or disprove the theory. One of my early mentors was adamant that it was fact and I saw no reason to dispute this. My subsequent experience has done nothing to indicate the truth one way or another. Like so many of these things, it comes down this; if you want believe it, go right ahead. GD
