Been there, done that. Tub of mixed surplus .45 ACP rounds and a couple of clueless shooters (I was one of them). Massive corn cob pile as a backstop. Burned for days.I never saw any ill effects with 30 cal. tracers. Like has been said just clean well after use. I will add, be careful with tracers because you can set the world on fire. Don't ask me how I know. LOL