Tunaman: rickt300 is right about action length. You should use a long action. I think the 7x57 is a gentleman's caliber, for alla you gents out there, and if I was going to build one it would be on a 98 Mauser action. Even if you only load a 140 gn boolet into the 7mm, the action length would be exactly what the col and the 98 action call for. If you ever decide to go up to a 175 gn slug you can definately load it long, if you need to, and never need to worry.
Here's an example:::: I have a Swedish 98 - it's a Husquarvarna sporter, a 98 action made for the 8x57. I loaded up a bunch of round for accuracy testing with some 195 and 200 gn bullets, loaded them long, and in loading both slugs to just kiss the rifling I found the overall length of the loaded cartridge to be longer than a factory 180 gn 30-06, which is a 62-63mm case length. I feel it is better to go with the longer action and, of course, the 98 action was made for the 7x57. Good luck and let us know how it goes. Mikey.