I bought a lightly used CK 9mm open gun from a forum member . The original owner said it ran very well. Now on a couple of different posts he is trashing CK because he said it never ran right. I have run 8 different bullets and 3 different powders thru it. I have put almost 5000 rounds thru it not one failure. One of the supplied mags had a problem. Called Aaron at MBX and he sent me a new follower and spring. Problem went away. I like it so much I bought another one. Should be here next month.