Of all the varmint and big game cartridges developed and introduced by Winchester, the 1963 vintage .300 Winchester Magnum is the fifth most successful. Only the .243, .270, .30-30, and .308 Winchestercartridges are more popular. The .300 Winchester Magnum is an excellent cartridge. When loaded with �bullets weighing 150 to 180 grains, it shoots plenty flat for deer size game at long range, and when loaded with 180 to 200 grain bullets it packs enough punch for cross canyon shots at elk and moose. Probably the worst that could be said of the .300 Winchester Magnum is that the recoil is a bit much for some shooters and it destroys a good bit of venison when used on deer at close range. But nobody who has seriously worked with the Winchester's big .300 has ever said that it is inaccurate. It is, in fact, a favorite of competitive shooters who try to put them all in the X-ring at 1000 yards. Most hunters who use the .300 on deer and pronghorn prefer 150 grain bullets, but a 180 grain spitzer shoots almost as flat and destroys less of the eating part. The single best load for elk and moose may just be the 200 grain NoslerPartition or 200 grain Speerbullets pushed to 2984 fps by H1000. 

This text is based on information from “Cartridges of the World”, Hodgdon reloading manual, the cartridge designer and/or own resources.