They are also often called 7mm saum or 7mm wsm but Lyman suggest that 7mm saum actually has an advantage in speed. Not a ton, but some. I can't see a reason other than speed that saum would be better. WSM are more popular as far as I know and I find more data and supplies for them.

Reason I ask is I gave a built gun on a short action. Had I known more about guns when I bought it, I would have got a long action in 308 so I had more options. Im having the idea that side ive spent so much time and money on bedding, inletting, stock, etc, I need to just stick with this action and gun as a whole. I can never get my money back on such a custom build. But the idea that I can stick a 7mm 300 wsm in a short action, sacrifice a little speed, and have very good ballistics and accuracy is tempting. I have the barrel in 308 right now. Id simply buy another barrel in 7mm 300wsm and use it as a swap gun.

Next gun I get is probably gonna be a 338 lapua which will be awhile and I understand the economics of it is terrible but the reasons for such a purchase or build are not necessary to discuss. Either way, Id like to be able to save money (for a 338 possibly) and have one gun in as many short action configurations as I like so if I want magnum performance, I'm going to have to go with something like a wsm or saum.