I've just spent the day shooting my CG 63 Swedish target rifle and what a thrill it is to hit a 10" by 12" target at 300 yrds from a standing position with a sling.
Two other shooters who had never shot 6.5 x 55 before (one a .303 Enfield and L1A1 fan and the other guy a FAL freak) both put 10 rounds each through the CG63 and said they WILL be getting one .... they were VERY impressed
To me, the "feel" of the 6.5 Swede round has a "right" feel to it .... I know that's a bit nebulous but I bet you, and others here, know what I mean.
I used to have an old Sierra reloading manual and in there was a wildcat load some guy necked down a 338 mag I tink to 6.5 and used it to win a 1000 yard competition. This manual was published in the 80's and there was very limited info.