Sir,
I expect to improve this case the body taper could be blown out, but in my head then you would have a 6.5-06. I am thinking it has a small following, although I think it would just be a frog hair's difference between it and a 270.
Of the 6.5 x 55, I am of the opinion that it is very underloaded, just like the majority of the military cartridges, because of liability considerations. I have a modern u.s. made rifle in 6.5 swede, and I am positive it is capable of "improved" level performance with some careful plusing up and graduateddevelopment. To be honest I don't have much interest in such a thing, as that rifle is heck for accuratte, and real easy on the shoulder.
This is a dandy little cartridge how it is, but I expect a fellow could get a 6.5-06 custom built, or find himself a 264 WIn mag if he were in the notion, and be pretty happy with such a thing.
Hope that it works out for you,
Steve