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

My 300WSM 8400 Montana is probably my favorite big game rifle. I know some don't like the "belly" the 8400 has, but it seems less pronounced with the WSM.

What issue bothers you Brad? I know you have tried many Montanas in various calibres.

If you want lightweight, and a .338 bullet through an elk at 400, the 338 Fed will likely do that fine with the 160, 185 TTSX or 180 AB as examples.

Lots of truth in this ^ I hunted with the Federal round since it first came out in 06 or thereabouts. Got rid of it last year when I picked up the RCM on a whim. IMO the 338 Federal is one of the best rounds to come along in recent history. I took a big bison with mine at 300 yards so I know it will take elk. I've never liked the WSMs, none that I've owned fed worth a hoot. The RCMs are much better in that respect.

Lots of good thoughts presented here. Its only 287 days till I leave for elk camp, come on elk season...............

I agree 338Rules, be sure the 338 RCM will not have issues in a magazine built for the fatter 300 WSM. If it works and the bolt face fit is not an issue give the 338 RCM a try.

The brass is once again available. Bruno's has it on sale:

http://www.brunoshooters.com/product/9778.html



I own two 338 RCMs. Own the SAMMI spec reamer too.

Built a tang safety SA Ruger in a now discontinuted McMillan Ultralight stock Rick sold me. 22" #2 Lilja. Had magazine lengthened to 3.1" for useful OAL of 3.050". Rifle weighs 7 3/4 lbs with scope. Killed two cow elk with the 225 Accubond velocity 2750 fps.

Recently made a super accurate load for this rifle with the 300 gr Berger:

300 gr berger seated to fit and feed from magazine
54 gr of RL-17 fed 210 standard primer virgin 338 RCM brass
Velocity 2349 fps (3675 ft/lb at muzzle)

I used information from from another site and the Berger's terminal performance on elk worked well as slow as 1966 fps impact velocity.

This makes this load viable out a bit over 600 yds!
@ 7000 ft:
POI Velocity Energy
100 0.5 2286.7 3482.5
125 -0.0 2271.2 3435.5
150 -0.9 2255.8 3389.1
175 -2.3 2240.4 3343.2
200 -4.0 2225.2 3297.7
225 -6.3 2210.0 3252.8
250 -8.9 2194.8 3208.4


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For grins I built a 14 lb LA Mark X with 29" 1 in 9 twist barrel in Joel Russo stock. This 338 RCM is long throated to shoot the 300 gr Berger at a mundane 2455 fps using It is a real hoot to shoot and bucks the wind quite well with lots of energy way out there. It can be fired 10 shots in a row and the barrel only gets "warm". Did use it once for a coues wt hunt. Shot a buck at 400 yds. .338 diameter hole through entire animal minimal meat damage.
Load data: fed 210 primer 54.5 gr RL-17 seated .010" into lands

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Some loads tried with the SA:

all loads use fed 210 primers

225 accubonds: worked up to 61 gr of RL-17 / 2750 fps with Fed 210 match primer.
180 nosler bt: worked up to 64 gr of RL-17/ 3045 fps.
215 sierras: worked up to 55 gr of Varget, most accurate 54 gr/ 2730 fps.
215 sierras: worked up to 64 gr of H4350/ 2865 fps

AZ that's the kind of info I was looking for. Thanks!

Was your Ruger SA just a plain Jane SA - meaning 0.473 case head bolt face?

It was a 243/ .473" bolt face SA tang safety Ruger. I had my gunsmith, Joe Reid at Harry Lawson co here in Tucson, open up the bolt face and lengthen the mag box. No other alterations were necessary to make it feed the 338 RCM.

I really like those old tang safety rifles, have two SAs and one LA all with lengthened mag boxes. Two have timney triggers, one to go.

The 8400 stock handles the WSM's recoil about as well as any stock can, but I just don't like the way the stock "feels"... it's "chubby and clubby" all around. I dislike a no.1 barrel contour, especially on a rifle with the recoil of the 300 WSM, and would prefer a no.2 contour for more weight out front.

I’m still drooling over that rebored 84L 338’06. What barrel length did you end up with ?

21" barrel. 6.75 pounds on the nose with a SWFA 3-9 on it.

Alaska_lanche, what FPS do you think it would shoot 210 Partitions?

Not lanche, but my 22” bbl’d 338-06 would go in the mid 2,700’s with the 210 NP.

Thanks. It occurred to me I never reloaded the 210 Partition in my 22” 338-06. Mostly 225s, and it seemed to be rather slow.

The 210 NP was my favorite bullet in all the 338 WM’s I had, and is the only bullet I ever used on the elk I killed with the 338. To me, the 210 Partition in the 33’s is like the 130 NP in the 270 Win in that it kills all out of proportion to its size.

Without a doubt. It hammers elk and penetrates likecrazy. It’s very accurate in my 338 as well and pretty easy to get up to the 2950-3000 mark without issues. Like Brad mentioned, it should’nt perform as great as it does.

I couldn't get the 210 NPTs to shoot as well as the 210 Sciroccos so I focused on the latter more. Final load was 2800+ fps with the 210 Scirocco. 225 Accubonds were at 2690 fps as well. I will be working up a 230 ELDX load as well. But for my brown bear tag on Kodiak this spring I will be using the 210 Sciroccos likely even though the 250 A Frames at 2550 grouped well too...the weight renetion on the couple 210s I have recovered were excellent and I am not worried about not making it to the vitals by anymeans.

Thanks! IIRC I was getting low 2600s with 225 ABs and Partitions using H4350 and RL17. Wish I would have tried 210 Partitions.

2730fps from my 22 inch barrel.

It's essentially the same speed as a 180 from a 30-06, 165 from a 308, 150 from a 7-08, or 140 from a 6.5 Creedmoor.

But we all know the Creedmoor is better

Take it from someone who actually owns a 338 RCM.

The RCM is not destined for the trash heap, not by a long shot. Hornady makes brass and it will be around for a long time as a niche cartridge for those who really know what it can do.

It is the equivalent of the 338-06 Imp, but in a shorter overall rifle.

My 22" Ruger 338 RCM weighs just a bit over 8 lbs with a Leupold VXR scope.

Burning RL16 61.0 grains I am twisting 250 AB's at 2,615 average.
RL17 61.0 grains will push 225 AB's at just under 2,800 mv.

It's a great cartridge and would rather be able to buy 338 RCM brass than neck or form 338-06.