Whoa! The 7x57 is in the 45,000cup range. It will most likely take your Contender apart at the seams with factory loads. It is nothing more, or less, than a 7mm08 with a .200" longer body. If you download it to safe limits(pressure), why not get a 7x30 and save yourself some headaches. Forget this barrel and get a 7x30 if you simply can't live without a 7mm.