IMHO copper is about a million times easier to completely remove from the barrel than lead. Granted on a on 2" snubbing with typical rifling it's not so bad but on many other types of firearms removing lead is a major pain. Barrel length and type of rifling of course are the major factors in how hard it is to remove debris but overall copper is easier to remove on any firearm. Yes, lead is softer than copper which is exactly the problem. The way I understand it, that is the reason why lead leaves behind 10 times more debris than copper to begin with.