It's the 225 Win. necked up to .308. A great creation of Rex Merrill, the inventor of the Merrill pistol, which later became the RPM when Jim Rock bought the company from Mr. Merrill.
It requires no fire forming, just a simple neck expansion. Mine is super accurate, and my everyday load runs a 150 @ 2250 fps ... it will do a bit more, if you insist on loading it up.
