I have often found myself yearning for a new chambering for no particular reason. I built myself a 7mm-08, on a Turkish Mauser, just because I liked the concept (this was when the 7mm-08 first came out). I liked the rifle. It shot great, functioned great, and was a very practical hunting rifle in all respects. So I changed it. It became a 6mm Remington, a 260, a 308 and today, it is chambered for the 8x57; just as it was in the beginning.
I like the 6.5x55 so I've had a few and presently have a fairly nice Mauser in that chambering. Given that I have the 6.5x55, one has to wonder why on earth I am in the middle of building a 256 Newton.
Anyway, I think you should go for a 7x57. GD
