Though this my first post to this forum, I've had a Contender for almost 20 years. The reason for this post is I'm looking for the formular to determine whether a caliber is safe to chamber in a contender. I had that information at one time but I can't find it now. As I remember it has to do with operating pressure of the cartridge and the area of the cartridge head. If anyone knows, I'd appreciate the help. Before anyone asks what caliber I'm interested in, I actually need the formula to reverse engineer a caliber conversion on a firearm made by another company.