I figured the title should be kind of generic but I'm starting off with cast iron. We are considering placing sewer lids at 100 to 300yds, obviously the shortest distance raises the most concern. What would you consider is a safe distance for these lids? Angled downward how much? What caliber is too large and unsafe at what distance? Edit: .30 cal is supposed to be the largest round used at this facility. Or, don't do it! The irregular surface will cause erratic ricochets that aren't worth the risk.