G1 BC of .718 at 2620fps, yes it outperforms many factory .300 Win Mag
Outperforms it how? Wind drift? Thats comparing projectiles not the cartridge that propels it. Drop to 1000m? Not a chance.
I'm sure someone somewhere is trying to claim their 300 win will equal a 300 rum in an apples to oranges comparison just like you are. And they're coming off just as foolish.