There is no major difference between them. From a sporting perspective, they almost indistinguishable. The 7x57 was once far more popular and the 6.5x55 seems to be enjoying a small resurgence. Both offer an exceptional balance of power and recoil, while delivering excellent accuracy and terminal performance.
Why did the Swedes build their own round? Might have been some kind of conflict or licensing concern, at the time?
just wondering why the Swedish didn't go with 7mm Mauser.