Has anyone here built a .257 Dakota? Results-accuracy,velocity, barrel life? Thanks,Frank.

Oh my god.
I'm sure you could get all the speed you wanted, with commensurate barrel life.
Somebody correct me if I'm wrong, but I believe one of the big advantages to large-capacity cases is that they can be loaded to much lower peak pressure within a given velocity range.
So you could have top Weatherby speeds without blowing your barrel out, assuming you can find the right powder.
It's your calling.
Do us proud!