Rocdoc, I'll attempt to give a short reply. Jamison had been promoting a short action series of cartridges he came up with for commercial purposes. Winchester introduced the 300WSM, and then the 270 and 7mm WSM's the next year, and then the 325WSM a couple of years later. By then Jamison brought suit against Winchester and Browning, claiming they had copied his idea for the rimless short magnum. Apparently, the defendants attorneys were not gun guys, and Jamison won the suit. He now gets a royalty on every one sold by anybody in a WSM caliber. Obviously, Ruger had better lawyers. They ceased production on all of the WSM's and RSUM's and partnered with Hornady to produce their own compact magnums, the 300 and 338. Had Winchester's lawyers researched the situation, they would have discovered a wildcat round of the 50's called the 30 Howell which uses the same short fat case design, a 348 Winchester with the rim turned down, blown out, and necked down to 30 caliber, which is more or less what the 300 WSM is. So any further development of the WSM's was ceased and shelved. I build a 358 & 264 WSM and my smith built a 375 WSM. I even had Hornady make a set of 458/ 325 WSM dies, but no rifle yet. Hope this helps. Bob!!