Generally anything fired from a .300 Wby will take a deer with a degree of authority. With my two .300 Wby's I use 165 or 168's on deer and hogs. It is the best of both 150's and 180's and if you use a Barnes, you are covered up to dangerous game. I have never used a Vanguard, so I have no idea how much free bore you are working with. My old Mark is a West German with about 3/4 of an inch of free bore, the other is an Accumark USA that has only about 1/4 inch of free bore. Both have 26 inch barrels, the old Mark (a 1 in 12) requires a hotter load to hit it's sweet spot. In my rifles I use a standard bullet, I shoot the 165 gr Sierra Game King HPBT. It will shoot about a 1/2 inch group everyday, if I do my part.
I use this load out to 500 yards. Old Mark: .300 Weatherby - Sierra 165 gr Game King HPBT, 79 grs of IMR-4350, Federal GM215M primer, Weatherby/Norma brass, Velocity - 3300 fps - checked with my Oehler 35P. (might be a little hot in yours)
Accumark: .300 Weatherby - same load, except 77.5 grs of IMR-4350, Velocity - 3225 fps - checked with 35P. (should be OK)
There a lot of good bullets that work in a .300 Wby, over the last 40 years I have loaded everything from a 110 gr to a 220 gr bullet, most shot well. The best group I ever got from the old MK was with a 180 gr Remington Bronze Point around 200 rounds down the barrel. The best group I have gotten out of the Accumark was with a 165 gr Swift Scirocco with a 150 passes down the barrel. Best of luck to you!
Good shooting,
Marcus.
