Home Forums Hunting & Shooting Hunting Rifles 300 WSM to 338 RCM - anyone do this?

I know where a Kimber 8400 in 300 WSM is sitting for a good deal. I have a 300 WSM in a Win M70 EW so don't need another. I've always been intrigued by the RCM cartridges. Case head is very similar but the RCM case has a slightly smaller shoulder diameter (0.538 vs 0.515). On the surface it would seem to work. Anyone ever re-barrel a Kimber, or any other WSM based action, to the 338/300 RCM? If so, how did it feed the RCM case?

A 7-7.5 lb 33 caliber rifle would be sweet for chasing elks.

Thanks.

Why not just find a SS ruger compact instead, rifle and scope probably cost much less and weight about the same.

CDNN has a few in stock for cheap

Why not just do the plain old 338/300 WSM since it probably works as is and you could neck up 300-325 stuff pretty easily? Not knocking your plan but the WSM brass is pretty danged easy to get ahold of.

CDNN used to have them for $399! Bought one in 338RCM and sold it like an idiot because I was concerned about finding components. It was a sweet little rifle.

^This. If the Kimber 8400 WSM mag is long enough this route is a no- brainer.

The 338 RCM was designed around the 2.8” Short magazine, and it’s case is shorter than the 300 RCM.

I believe ( but haven’t verified) that the Ruger, Kimber, and M70 short actions are actually a tad longer than 2.8” .

Are you thinking of necking up PRC brass for this cat ?

You could probably try cycling a few rounds of 300RCM or 6.5PRC through the Kimber to see how/if it feeds before committing to one chamber or another.

At one point I considered extending the chamber of a 338RCM to the 338/375 length & slapping it onto a long-action .Didn’t really make sense, even to this loon, as the SS barrel that I had was only 20” . Probably a tad blasty at that length.

Woefully, I don’t have it now, mostly because of ammo availability issues.

The case head above the grooves are .532" for the RCM and .555 for the WSM. I'd stick with the WSM or get a rifle chambered for the RCM from CDNN.

I keep looking at those cdnn 338 rcm.....so far Ive managed to not buy one. The stainless synthetic version with open sights looks like a blast!

To elaborate a bit more on my idea. The goal is to build a rifle that weighs 7.5-7.6 lbs with scope in a cartridge that doesn't recoil as much as a 338 WM. The scope I want to use is a NightForce SHV 2-10x42. I've shot a couple sub 8lb 338 WM and will pass with full power loads. I've considered going the traditional 338 WM route and loading it down.

I also like the Kimber MT platform - it fits me well, stock and action are both solid performers. The Kimber MT WSM platform weighs 6lbs 3 oz bare rifle, NF and Talley 30 mm rings adds 23-24 oz to the mix. Rifle weight ends up being ~ 122 oz or 7.6 lbs. Install a 22" barrel and it comes out right at 7.5 lbs.

The 338 RCM is an oddball no doubt about it. But it has the same capacity as the 338-06 - which means it can push 338 cal bullets to meaningful velocities. I'll chamber a rifle around the 210 Swift Scirrocco and/or 185 TTSX. Both bullets launched from the 338 RCM platform should perform well to at least 400 yards.

I've looked at the Ruger Hawkeyes. I love the Ruger 77 in all its versions and have owned a bunch. The issue is weight. Both the 22" and 20" SS All Weather will weigh right at 8lbs with a Leupold VX-3, 8.5lbs with the NF SHV. The goal of this rifle is elk, backpack and dayhunting. I've dragged enough 8+ lb rifles around at 10,000 ft. I'm 55 and the mountains aren't getting any flatter. I've been using a 270 and 308 the past several years with success but have shot the last 3-4 elk at less than 50 yards in the timber and not broadside. I like 2 holes in animals and have test loads with various Barnes bullets for my 308 and 338 Fed to try. If the 338 Fed works out, I likely wouldn't do a 338 RCM. Or maybe I might to have a pair of elk-capable rifles.

Scott - on the 338 WSM, I considered that as well. Where to get a reamer? Could it be as simple as sending my current 300 WSM to JES for a 338 re-bore? Its been sitting in the safe for years. Using a Leup VX-3 I have and aluminium bottom metal, I could get it down to 7.7 lbs give or take an oz which works as well. If recoil gets too stiff, I can load it down a bit. I only have about 500 pcs of 300 WSM brass............

338 Sherman short. Look on Sherman short mag seb site for solid information. He rents dreamers. Good luck

I highly recommend the 338 RCM in Rugers compact platform.I found a left hand version and have been using it for about a year now. So far I've taken a big bull bison, a caribou, and a wolf. I have access to one small sporting goods store and have had zero problems getting brass. I have enough hoarded away now to last as long as I will be hunting. I cant imagine a better all around caliber for big game.

Get the Kimber 300 wsm and hunt it as is. 155 Scenar, 165 Game Changer, etc. If you really want to spend some money, I'd be going smaller in bore diameter into a 7 or 6.5 rather than up.

To Calvin's comments, in the 300WSM, the 150 Barnes TSX or TTSX would be better close range elk bullets than the Scenar or Gamechanger.

Or if you can find them, the Winchester (Combined Technologies) Fail Safe would punch though an elk from any angle. The only one I ever caught out of my 338WM, was diagonally through an 80 yard bull moose on the second shot (I was shooting until it fell over, we had already tracked him 8km measured on the map). The bullet broke the onside hip, went through a full belly, the lungs, offside ribs, shoulder blade and was found under the hide at the front of the shoulder. Outstanding performance.

If I wanted a lightweight 338 I’d build a 338-06 or 338” WM.

While almost no actions handle the WSM’s as well, I have no love for the Kimber 8400 MT.

The 338 RCM is destined for the trash heap of history. For me, I can see no reason to go there, and I’d take the 300 WSM over the 338 RCM every day no matter the platform.

It's obviously all a matter of opinion. Hornady has a habit of supporting their offerings. It could very well be the opposite, that the 300 WSM (like all the other WSMs) will be in the trash and the 338 RCM will go on. I doubt anyone here will be around long enough to find out.

B, my opinion is send it off to Jess and let him do his work to the rifle. You’ll be into it 225 bucks and a set of dies. Anneal the brass and shoot it.

I’d be prepared to lap the barrel decently and DBC it but that’s about it. JES will find the reamer for it. I’m betting it will just be a straight rebore though. I think it’s an excellent idea and a butt kicker of an elk rifle.

Seriously?

Universally, the 300 WSM is the most successful new cartridge offering of the last 50+ years...probably only to be eventually eclipsed by the 6.5 Creedmoor.

Agreed....I had a portly feel 300 WSM for a hot minute and just never could warm up to it.


Which is exactly why I went for a 338-06 off the 84L.

Plus then you can put nearly any scope you'd desire and still hit your 7.5 pound goal.

I agree the 300 WSM is here to stay as well. In fact my latest rifle is in such cartridge. It shoots the same weight bullet roughly the same speed as my 338-06 but is a full 1.5 pounds heavier than my 338-06 and 1" more barrel.

No, not really. I fully expect the 300 WSM to do well and hope the RCM becomes more popular as well. It's just that things in life often take the unexpected turn.
Happy hunting!