Does anyone know anything about this cartridge?
sources of brass, load data, or dies and such?

PaulS

This is a new one to me! What is it, an 8X60S necked down to .257"?? Or some other critter??

eldeguello,
I am unsure of its origin but the base is the same .473 as the 243,270 and 3006. It is 2.323 head to mouth and the shoulder is at 28 degrees and begins 1.85" from the base. It only tapers .030 from base to shoulder. If it is a wildcat I would be surprised.

PaulS

It's listed in the Wildcat Cartridge Book Vol II. Its a 25-06 shortend. The length is about half way between a 257 Roberts, and a 25-06. It got it's name because the USA was supposed to switch to the metric system. I'm guessing it was made in the late 60's or early 70's.

The write up in the book was by O(T?) Winters, I think. Supposedly a more efficient 25-06 (at the time).