So it being born into the world as a target cartridge and being loaded with various bullets designed as long range target bullets doesn't count? Hmmm Well it would be a heck of a metal silhouette cartridge for sure. As for being designed as a target cartridge chambers often have tighter throats, freebores are usually configured for match style bullets and shoulders are often sharper to extend case life and make for more consistant headspace. Does that sound like the 6.5 CM to you?
The reason the 270 has generally a 1-10 twist being that flat based spitzer bullets of a weight commonly found when it was designed were not all that long and round nose bullets were very popular at that time also. Optical sights were not especially common back then either and those that were available could be considered crude with generally low magnification.
I have 3 270 rifles, all three are fine shooters. My least accurate is an Encore, this from a tracking test of an old Bausch and Lomb scope.
These two targets were shot with rifles that had match chambers.