I think you would have to get a metallurgist to give you a definitive answer on this as it is a very broad question in the sense that many variables could be introduced that would affect the correct answer. I do know that most barrel makers consider CM stronger than stainless (try to get Krieger to make you a pencil barrell in stainless.) However, I think this is consideration of tensile strength for safety reasons and not erosion resistance. Obviously, the conditions under which the rifle is fired is another consideration as well as numerous other factors. When all is said and done, I believe heat, bore smoothness and cleanliness are major factors in barrel life.
