I keep hearing folks refer to the 300 WSM as a round falling somewhere between the 30-06 and the 300 Win. Mag. If this is true then either I am grossly underloading my 300 Win. Mag, or grossly overloading the WSM.

With a 180-grain Grand Slam and 69 grains of Re. 19, I am getting 3,030 fps. I feel like that's a little hot, so I have cut the load back to 68.5 grains of Re. 19, and get just a shade under 3,000 fps.

With the Win Mag. I shoot the old-tried-and-true load of 75 grains of H 4831 behind a 180 Grand Slam. This load chronos at 2,970, which is the same, or a little less, than the WSM. In some books, this is the max Win Mag load. In others, it's a grain light.

So my conclusion is that the WSM and 300 Win. Mag are equal.

Anybody else load both and had similar experience?

a buddy bought a featherweight in 300 wsm the first season that it was available. we then took it to the range, and shot it over my chrono, with factory loads, after getting it sighted in.

2963 with 180grs, factory, on about a 70-75 degree days. This is 7 fps slower than claimed by winnie, but .2% difference is not significant.

I get 3085ish with my 300 winnie, a remchamberd 1903, with a 23.75" barrel, with rl22, and 180gr barnesx

jeffe

I was always able to get 3150 to a bit over 3200 with 180's in my 300 Win Mag depending upon bullet type.

So the answer is yes, you are underloading your 300 Win Mag.

My hottest load for my .300 WinMag is the Sierra 220gr MK at 3000fps. The 180gr runs 3100-3200fps.
But I usually don't load this hot, due to the shorter caselife, and I don't really need the extra speed anyway...

In individual rifles, the WSM may actually be as powerful (or fast) as the .300 WM, since rifle barrels vary in actual diameter, slickness, etc.

ON AVERAGE, however, the .300 WM will outpace the WSM by 100 to 150 fps AT EQUAL PRESSURES with APPROPRIATE powders. Regardless of the shape of the cartridge, the cartridge with the larger effective capacity will provide higher velocities.

That being said, as a new cartridge, the WSM is loaded by the factories at significantly higher pressures than the .300 WM, erasing much of this advantage in factory loads. In fact, anecdotal information suggests that peak pressures in WSM ammunition frequently exceed normal working pressures in some rifles and give trouble with extraction. Look for WSM factory loads to "ease off" over the next couple of years, at which point they will run about 100 fps behind the "long" WM. This practice of "uploading" an newly introduced cartridge, then backing the pressure and velocity off later is a long-standing one in commercial ammunition manufacture.

Very well said Stonecreek. Another point is that some are testing both in 24" barrels when a 26" is preferred for the winnie.

My 300 WM from a 24" tube gives 3165fps with a 180gr nosler. There are no pressure signs. These loads shoot half to three quarter inch all day.