Re: 30-338 WM or 300 WM? Which would you choose?
I've used a combination of the two.
A .30-.338 Keele (long neck) version was what my current 1000-yard match rifle has for a chamber. Cases are made with .300 Win. Mag. ones full length sized in a standard .30-.338 full length sizing die. It's got about 15% to 20% longer barrel life than a standard .30-.338 made from .338 Win. Mag. cases. And is just as accurate. It's more accurate than the .300 Win. Mag,, but only marginal, just like the standard .30-.338.
All things being equal, either .30-.338's easier to shot accurate as it's got a bit less recoil than the Win. Mag. version. That's more important than the .300 Win. Mag's slightly better wind bucking ability.