I own and like my 300 WSM, but all of the WSM cartridges are largely misunderstood. The man who developed the 300 WSM never meant for it to have the "magnum" label. It was meant to be an improved, modern, short action 30-06 coming close to 300 WM speeds, but with much less recoil than the standard magnums. They were always intended for smaller, more compact rifles like the Kimber where the recoil from a standard magnum would be too much.
It matches and exceeds my 300wm with 180g bullets.
Only if the 300 WM is loaded with anemic loads. The hotter 300 WSM loads will somewhat overlap mild 300 WM loads, especially with lighter bullets. But the 300 WM if loaded to its full potential will always be faster by 50-100 fps. And the heavier the bullets, the greater the advantage goes to 300 WM. But that is irrelevant since it was never intended to compete with 300 WM, but 30-06.
A gun writer named Rick Jamison developed a wildcat round he named the "300 Jamison" in the 1990's and approached Winchester with an offer to sell his patent to them. Winchester declined, but came out with the 300 WSM shortly after meeting with Jamison. Jamison sued claiming patent infringement and won. This is the biggest thing holding back all of the WSM's. As part of the settlement any manufacturer making WSM rifles or ammo must pay a royalty to Jamison for a specified number of years. This means they either must charge more, or make less profit on anything WSM. I'm not certain of exactly when, but there are only a few years left on the settlement. I expect the WSM's to see a resurgence when more manufacturers start making them. Ruger and Remington developed their own "short magnums" specifically to avoid paying Jamison.
The 270 and 7mm WSM's in theory do the same thing with 270 WCF and 280 REM that the 300WSM does with 30-06. But the 7mm WSM simply never caught on. Nothing wrong with it, but it was too close in performance to the 270 which was far more popular. The 325 WSM was a disaster from the beginning. There are no decent 32 caliber bullets and the 300 WSM loaded with heavier 200-230 gr bullets easily beats the 325 WSM. A 338 WSM would have been a better option, but even it's advantages over the 300 would have been minimal, if at all.
The 270 WSM offers 270 WCF performance in a smaller, more compact rifle, which was Jamisons primary reason for developing the round. But velocity wise it offers VERY little speed advantage. I've never seen a 270 WSM load that beat what the 270 would do by more than 50 fps. My loading manuals show 270 WCF loads faster than the 270 WSM loads in the links provided.
The 300 WSM beats 30-06 by 100-150 fps with 180's or heavier, and as much as 300 fps with 150-165 gr bullets. I have no idea why the 270 WSM won't do the same. The case holds more powder, it should be getting better speeds.
Not knocking the 270 WSM. It is a good round that offers some advantages over 270. And overall think the WSM case design is a solid, but misunderstood idea. Winchesters decision to give it a magnum label probably hurt rather than helped.
