The 300 WM can be improved by eliminating the problems it has with too short a neck, throat and magazine box. Also the cases suffer web damage upon firing as headspace is in the wrong place.

Enter the 300 WM Improved. What is needed is a true magnum length action. The chamber will be cut to use 300 Weatherby brass that is sized to fit the chamber in a 300 WM die. Thus the neck will be long, the throat will be just right and the cases will fit the chamber on the first shot.

Factory 300 WM cartridges can still be fired in the rifle so it's an improved chamber.

I have to adjust the LOA of the neck later but time does not permit this refinement.

Sounds very close to the .30/8Mag.
Guys who talk about the "short neck problem" of the 300 Winchester have either never owned one or don't know how to reload. In rifles with a short mag box it can be a "short mag box/long throat problem" but the length of the neck is not an issue. The 300 Win Mag Sendero that I put together last fall shoots 1/2 to 3/4 with loads for my 300 Win Mag hunting rifle. Just think how it would shoot if the the neck were longer!
"Also the cases suffer web damage upon firing as headspace is in the wrong place"....see comments above on reloading.

.300 Jarret is teh 8mag necked to 30, but who needs that much boom? Lots of smiths will chamber for .30-.338. It was one a favorite in 1000 yd, competition. Long neck & if you throat it out just a bit (because who needs anything smaller than a 165 or 180 in a .30 magnum) it will equall the .300 Win accross the board, w/ about 1 or 2 grains less powder.

Or just buy a 308 Norma Mag, same thing but with factory ammo available. - Dan