I realize that the question pertains to auto-loader use, but my experience with aluminium in a .357 revolver was not good. The cases seemed to expand due to heat and locked up the revolver to the point where the swelled case would not allow the cylinder to rotate. Had to wait for it cool before I could even open the cylinder. Since then, I do not use aluminum for anything. Steel, okay. I'd use brass or nickle if I reloaded, but I due not reload.