I would opt for the 338 Wincheter if I was going hunting in Alaska for Grizzly bear. I might go for a 375 H&H for the same reason.

 

Personally one of my next purchases will be the .338 Lapua.
Now that there are a lot of manufacturers making rifles in this cartridge.

Availability is going up and the prices are coming down.
It seems to be really catching on for what was once considered a wildcat round.

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The .338 Win. Mag. and .338 RCM are ballistically similar, so the important factor would be ammunition availability (unless you handload). The .338 Win. Mag. is easier to find, especially in Alaska where it has been popular for 50 years or so.

As for magnums with 20" barrels, I am no fan. The muzzle blast is significantly greater than that from from a 24" barrel.

mbogo

 

I'm getting the ruger guide gun with a 20" barrel and want it in 338, just not sure if I'm better off getting the RCM or the win mag. Not sure which will perform better from that barrel.

 

If you believe Hornady's marketing the .338 RCM is specifically designed for 20" compact rifles and will preform better than the .338 WM with a 20" barrel. They also claim better temperature stability.

I have never tested the two to see if the fps difference is true and really enough to make it worth the downside to having a rifle in a boutique cartridge.

For this priviliage you will only have 2 factory loads to choose from, limited ammo availability, and increased ammo costs. You can reload it, but unless you're already set up to reload this will be expensive to start and would not pay for itself anytime soon unless you load other cartridges.

I own a .338 WM and it will easily handle any NA big game out to ethical hunting ranges. It will also handle any African plains game and leopard. The additional 4" of barrel doesn't kick my a$$ either.

 

Is 4 more inches of barrel really gonna add that much bulk and heft to a rifle?

That being said I would take the extra four more inches of barrel and use the 338 WM in a heartbeat. In fact I own a Rem 700 in 338! I don't know about you but I see a lot more 338 WM than I do 338 RCM on the store shelves...just saying. Plus why settle for two factory loads in the RCM when there are several that can be had in the WM? I am with 0002S on this subject.

 

If I may, what are you going to be using such a rifle for?

May help us make our recommendation? Are you planning to reload or just buy loaded ammunition?

 

I want to use it for bear, moose, elk maybe. Perhapse take it with me to Canada for bigger whitetails. And I plan on buying factory ammo, and I know it's limited but I'm okay with not being able to find it in stores. Once I get it sighted in I'm buying several boxes and that's it. It won't be my fun range gun where I go and blow off dozens of rounds. I already and a couple .308s and a 30-06 among other guns that is plenty for that type of hunting but I want a bigger caliber. And I do want that rifle in a 20" barrel. Just wondering what will perform better from it, RCM or wm.

 

And I do want that rifle in a 20" barrel. Just wondering what will perform better from it, RCM or wm.

On paper and googling chronograph data, with factory loads and same bullet weight, the RCM is around 150-200 fps faster in 20" barrel.

Nobody I could find seemed to able to duplicate the Hornady factory loads velocity and all the handloads were identical to .338 win mag velocities in a 20" barrel.

In the real world of shooting live game, 150-200 additional fps won't be noticed by the animal. Neither will make up for poor shot placement. Both will effectively kill the game you plan on harvesting at ethical hunting distances.

Since none of the limiting factors of the RCM effect your needs, I say get the RCM and enjoy.

 

You can load a .338 Win. Mag. using RL-19 (or maybe IMR-4350) so that it will achieve similar velocities in a 20" barrel, but you had better know what you are doing.

mbogo

 

The RCM will out perform the WM in a 20" barrel, that's what it was designed for. The questions now are, does 4" less barrel really help you in the field or does 200 fps make the WM too little of a gun? I would personally go with something like the Kimber Montana in 338 WM instead of the Ruger you're talking about. The Kimber will have a 26" barrel yet only be 4" longer overall and will weight just over a pound less than the Ruger.

 

Get the WM.

 

Get the WM, been around for awhile, not going away anytime soon. The RCM while it looks interesting, it may just be a flash in the pan story.