You would have to have someone cut the chamber to accept the rim, BUT like all rimmed cases in the Contender/Encore, you will still have to size cases to headspace firmly on the shoulder in order to obtain any accuracy, rim or no rim. In other types of single shots, the rim would aid extraction, but T/C got their extractors working fine years ago. As suggested the 7x57R would be much easier to form. Truly no mechanical advantage at all with several shortcomings (base brass & forming) but, like my mother said, if it will make you feel any better, just go on and do what your going to do anyway.