Some of the best ammo I've fired through mine was Czech from the late 40s. I've never had a problem with it. The only downsides are that it's corrosive and steel core, so you have to be careful shooting at plates. Unfortunately you can't really find it anymore. Well... you can because I have some listed on the trader, but outside of that, it has all but dried up. A lot of it was imported on WWII German clips.