Two things I noticed in the original post. First-forget about that "center of mass" term since shooting a deer COM will result in a gut shot. Second: most of the non-Wby ammo is rated at lower muzzle velocity than the Wby stuff. This coupled with the barrel length of the Vanguard puts you right in the same velocity ballpark as the 300 Win Mag. The reason=many of the Wby muzzle velocity figures are produced using a 26" barrel. Unless I'm seriously mistaken, the Vanguard has a 24" barrel(my 257 WBy does) which costs some speed. Cou[pled with the reduced velocity of the "aftermarket" ammo, you now have a louder, harder kicking 300 win Mag.
Not trying to poop on your parade, just stating some facts.
I've been considerably disappointed with my Vanguard 257 Wby as it doesn't show me much improvement over a 25/06 w/24" barrel while burning 15% more powder.