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.
