Someone left a stack of Alliant Reloader’s Guides at our range so I took one. For various cartridges, the data included one load for each one of the appropriate Alliant powders and Speer bullet weights, using Federal or CCI primers, since ATK owns all four companies. It didn’t say whether the loads were maximum or what.
For 180 grain bullets, three loads for the .300 Weatherby ranged from 2990 to 3109 fps, averaging 3058 fps.
Five .300 Winchester 180 grain loads ranged from 3050 to 3110 fps, averaging 3070 fps.
There was one .300 H&H load, 2996 fps. Three .300 WSM loads averaged 3006 fps.
In other words, they claim no difference between the .300 Weatherby and the Winchester and only a 50 fps or so advantage for the Weatherby over the H&H or WSM.
Can that really be true? No difference between .300 WBY and .300 Win? Besides, when I worked up loads for my .300 Weatherby both Hornady and Sierra handbooks showed 3200 fps with H4831.
The loading data is rubbish.
A chronograph will prove it.
One does not buy a .300 magnum for mild loads. For the amount if times it gets used on game, it offers a lot more that most reloading manuals indicate.
Expect a 180grainer to deliver around 3100-3150fps even in 24" barrels and a .300 Weatherby another 100fps more.
The value of the Winchester is a more common tendency for a very decent level of accuracy and also be a top velocities with H 3350 without going to the slower powders which can shorted barrel life if that is a concern. The extra volume of the Weatherby case will need those slower powders to gain that additional velocity as well as the longer barrel.
Both cartridges are great if you have a good barrel and can handle the blast and recoil though I think blast is a greater factor for the user.
