Holy smokes. There are no ethics involved with brass.
Actually, when you think about the resources used to melt it down and reform it into something else (maybe just pistol brass once again), it's very wasteful to scrap it rather than just cleaning and reloading it. Some folks think wastefulness is immoral / unethical.
John 6:12 - And when they had eaten their fill, he told his disciples, “Gather up the leftover fragments, that nothing may be lost.”