Yeah it's exposure to high temp/pressure gasses that eats the steel away in the throat that is the primary cause for accuracy degradation. Pressures are more or less equal between heavy and light bullets. More energy required to move a heavier bullet faster goes primarily to the type/amount of powder used....
For example,
If you shoot a heavy and a light bullet with the same powder you either run at the same speed with the heavy bullet generating much more pressure, or a the same pressure (less powder) with the heavy bullet going slower.
So I don't believe the issue is that heavy bullets cause more pressure. There may be something to bearing length because the rifling has to engrave more bullet, but I don't know how you'd conduct a "fair" test of this subject.
Changing powders changes burn rate and temp, keeping the same powder you have two different charges (different amount of "fuel") OR you have different pressures keeping the same charge (obviously whatever is safe for the heavier bullet).
Then potentially bullet geometry plays a part so you'd have to use a bullet with the same jacket but different core size. Interesting subject... My gut says that lighter bullets with more charge of faster burning powder is going to be worse for barrel life, pressures being more or less equal, but it's just a guess.
Another interesting question is what effect bullet geometry has. If a flat base bullet gets more barrel life than a boat tail or visa versa.
