Shawn pretty much hit it on the head. The lacquer is the issue when it gets hot. I've had the most problem with Wolf on this. I will say I have shot probably thousands of rounds of Tula .223 without problems. I believe they use a polymer coating as does some of the newer wolf. Steel case doesn't have the negative stigma like it used to. Especially when you consider that companies like Hornady make a training version of their 75gr TAP ammo that is the exact same bullet in a steel case. Great accuracy, same POI as my defensive TAP round, and reliable. I don't hesitate to shoot steel (but cleaning does reduce any chance of issue).