Probably a stupid question, but for what use do you intend this rifle?

I don't really want to spark a debate here, but - in my opinion - either of these cartridges are considerably overpowered for deer. Over the years, I've watched the .300-.338 magnums turn many good shooters into "flinchers." Combining opinion and observation, unless you're intending a western (elk) hunt or a moose hunt, I'd look instead for something from .270 to .30-06. If you MUST have a "magnum", the 7mm RM's already been mentioned here.

Regarding short- versus long-actions, most hunters can't capitalize on any weight savings afforded by a short action because it's really minimal, and any weight savings is quite often more than made up by too many Big Macs around their midsections. Yes, you might gain a bit more barrel length out of a short-action, thus negating any weight savings, for a very modest gain in velocity. Want a light action with a long barrel? Find yourself a Ruger No. 1.

I don't/won't own one, but everything I'm hearing at the range from those who do and who speak of it objectively is that unless you're reloading (and all of them do), there's not an appreciable advantage in the .300 WSM over the old .300 WM. The remainder of my range contacts are with guys who can cite almost every marketing point from any ad that's ever been published about their spiffy new .300 WSM.

I have plenty of guns I use for deer. My need for a 300 WSM would be to have something different with a different optical setup used for elk out west which could be used for longer shots if ever needed. A few of the gun makers have a shorter barrel that goes with the short action WSM caliber and results in a little lighter gun. While hiking all day in and out of the steep canyons of the west at altitude, having a slightly lighter gun makes a difference. My present elk set up is a Ruger model 77 Ultra Lite in 30-06 with a 3X9X40 Zeiss scope. The bare gun is about 6 pounds and I would like to get something a bit more potent without much additional weight. Besides you can never have too many guns.

it's an elk gun out west.....not deer as you assumed.....

I'm going with the orginal. if you look at published velocites on the wsm they are stated from full lengh barrels, good luck finding a 24-26" wsm barrel. the orginal is all 24-26" so in the end i bet they are even closer in speeds.

I was thinking about a Browning X-Bolt Composite Stalker.
I like the tang safety which is similar to my Ruger 77UL.

300WM
26" barrel
46 3/4" total length
6 pounds 13 oz weight


300WSM
23" barrell
42 3/4" total length
6 pounds 8 oz weight