I'm not even sure this is a debate.
300 win mag hands down with a Berger 215 Hybrid (.696 bc) at 2850 muzzle velocity.
338 win mag and a Berger 250 Elite Hunter (.682 bc) at 2750 muzzle velocity.
winner is easily the 300 win mag that pushes a higher b.c. bullet faster than a 338. Flatter trajectory and less wind drift.
Although I love the 338 win mag, it just doesn't have enough horsepower to push the heavy/high b.c. bullets fast enough for a 1000+ yard application.
At the ranges you mention it is all about the wind and therefore I contend all about bullet BC. I think you should forget the Win Mags and consider the RUMs as in 338 RUM. The 300 grain Berger with a BC of 0.818 is THE bullet.
The .338 WinMag is anything BUT a "Vega".
I owned one...Trust me, compared to the other .338 calibers with case-appropriate capacities....It's a Vega. Get a RUM, Edge, Terminator, Lapua or something of that nature if you want a .338. The .338 WinMag is not a hotrod caliber.
I can find .338 WM, RUM, and Lapua at my local shop. They even have .50 BMG, Nitro Express calibers, and all sorts of other odd and end stuff. They're a small shop, but their primary sales are guns, ammo, and reloading equipment and supplies. So they have VERY thorough and large selections for those.If I cant walk to the local gunshop and buy a box of ammo..then I dont want it!
Now which one of these...RUM, Edge, Terminator, Lapua can you find in your local gunshop????