Hi Kirk, you probably will be OK; most factory ammo comes in at .012-.014 anyway. But just to be safe you might want to make a cerrosafe cast of the chamber and compare it to a loaded round. That's not a bad idea to do anyhow, to see how big and how long your throat is, especially if you're going to shoot any cast bullets through it. I've got to do that to my new 6X47 for the same reasons - I don't know if it's got a turned neck chamber in it or not. The fun of getting an old bench gun going after the last owner has died - I can't ask any questions. Hope you enjoy that new Zipper!