chambered221 wrote:

Looking at Remington and Winchester factory ammo specs the 300WSM beats the WM in velocity with 150 and 180 grain bullets. (within 100 fps).

Could be not going to argue that. But I'd suggest getting chronograph and taking readings, your in for a surprise.

Dimitri

You may be surprised with any factory ammo not just the WSM’s !!!

I have chronographed factory ammo because I’m aware of the difference one might see.
One reason is due to difference in barrel length. Most all factory figures are taken with a 24” barrel.
A second is how we measure the velocity. Sitting a chronograph 10-20 feet in front of the muzzle does not give the muzzle velocity. Factory ammo is either measured from the muzzle or corrected to the muzzle.
Another possibility that can change things drastically is when the factory uses a pressure barrel to take the readings.

And lets not also forget variables such as air density, bore condition, and as some around hear have alluded to, our position in relationship to the equator !!!

True enough but I am talking about comparing the 300WSM and the 300WM side by side, since the WSMs came out it seems that the vast majority of reports are that they come up short when compared to the full size Mag calibers.

Dimitri

The list of chamberings that came up well short of 'as advertised' is much longer than the list of chamberings that ever exceeded.