RE: .204 Ruger?
Well, generally its not barrels that wear out but the throat area. And thats due to powder. Sure the bullet size has an affect, but the more powder you dump, the faster it wears out. You can take a 7mmRemMag, and a STW, and you can load up so both shoot a 140gr bullet 3000fps, and it will take more powder in the STW to do it, and I guarantee you the STW wears out first.