I have been thinking about converting my mosin nagant to 358 cal. I would be using the original cases just necking them up, I have heard of 9x56 or 57, is that what it is? also I would be shortening the barrel to maybe 24" ( it is a 91/30), since that would cut the thinner walled part of the barrel out could it just be bored out or is this a new barrel situation. if I will need to replace the barrel how expensive/extensive of a job is it, I know it would be a gunsmith job. alright thanks a lot, Travis