I would like to mill 0.20 off the 338 RUM sizing die and neck up to .358, cutting it off at 2.62 inches. This 358 Short Ultra Mag (358 SUM) will fit an '06 length action, just as the 300 Win Mag does. The available .358 bullets are not long for their weight and ogives are gentle, so seating will not be overly deep. Usable case capacity will match or slightly exceed the 358 STW, but it will go in a shorter magazine, do away with the belt and eliminate fire forming.

Comments and criticisms please.

Sabot, I've always liked the .358 calibre, definitely sounds like a worthwhile project. What bullet weights and shoulder angle are you planning?

Savage -

I would like to keep it as simple as possible and leave the shoulder at 30 degrees. A 12 inch twist rate will handle everthing from 180 to 320 grains, but the bread and buttet weight will be the 225s. Should have 95 grs of usable H2O capacity at COL 3.340 with Nosler partitions, capable of a bit over 3100 fps.

Something like 55 grs of XMP 5744 should push 200 gr Hornadys 2750 fps for a deer load, and .357 pistol bullets at 2000 fps can do varmint duty.
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You're going to be doing some swaging all the way down the body, so you might check the math and see how much you'll squeeze the bottom there. Too much and you compromise the web strength. And from what I understand, you should never try to anneal the bottom 1/2 of the case, so there's no help there.
But assuming that doesn't give you trouble, it sounds like a fairly simple way to duplicate the 358-300 Dakota. But with this one, you'll have more taper (5.25" at shoulder as opposed to .531"), and a body that is a whole .044" longer. Plus all the fun a rebated rim brings!

(I should mention I'm a biased fan of the 358-330 Dakota, so take this with a heaping tsp of salt.)

[ 07-09-2003, 21:51: Message edited by: Bwana-be ]

You might as well chamber for the .358 Norma Mag. This is the most practical choice, unless, like me, you prefer a beltless round. You might consider a .35 Newton as an alternative. You can form from readily available .338 Win. Mag. brass or 8x68s.

I would just go ahead and use the full -length .338 RUM case if using an action long enough to take it , which could be any M-700 or M-70 . If using a shorter action , I would go with the .358 Norma .

Pushing back the shoulders on the RUM case would be alot of work , in my view. I think the .338 RUM is a very nice case as is ........

Thanks guys...the 358 300 Dakota wins this one. No belt and more capacity than the 358 Norma.

I agree that the 358 RUM is super and very easy to make - Squeezing down 375 RUM is the best to retain neck length. The difference between 3.4 and 3.6 inch actions is not worth worring about. However, the round becomes so powerful that you wonder what you would use if for that would not be better taken with a 375 RUM.

For the record, the swaging problem does not exist for the 358 SUM, as we are only pushing the shoulder back 0.10 from 2.296 to 2.196 - the 338 RUM is shorter than the other RUMs.

Dang it...now I'm talking myself back into it!! Is there another 5000 FPE round out there that fits a 3.4 inch action under .458 caliber?

[ 07-10-2003, 00:15: Message edited by: Sabot ]

Seriously, have you shot any of the medium bores generating 5000 FPE? From what I've heard, and my experience with the 350 Rigby, I'd say the search for an extra 100-200 fps comes at a steep price in terms of recoil, with precious little gain in trajectory or terminal performance. IMHO, if a 358 Norma isn't enough gun, then go up to a 40 caliber, which definately is more gun.

I have also lost any desire to fiddle around with or form brass, something else I've learned with the 350 Rigby. There is something to be said for std calibers, but I certainly understand the appeal of wildcats.

Paul -

I'm looking at a case with 97 grs water capacity and 100% load density giving 3162 fps with a 225 gr .358 for 51 FPE recoil in an 8.5 lb rifle. No love tap, but quite close to my 338 RUM with 225s which needs only a premium recoil pad to be tolerable. My 416 Rem at that weight is 71 FPE...about 39% more.

Still, I get your point...the 416 is far more effective with the increased SD weight and cross section and well worth the push when you need it.

first...

358 bullets at 225 have an SD of .250... perfect for whitetail, horrible for africa...

I am a HUGE 358 fan, as I have 3, right now, and believe it to be the perfect north american round.. hell, anywhere other then africa.... 225 (bc of .422) at 2500 has the same ballistcs as the 308 LC match, down range, within 5 inchs at 400 yards.

Making it go MUCH faster is just a waste of time, in that a 225 would just come apart that much faster..

now, a 300 at 3000... there's a penetratin mo-fo.

back to this, I have often thought that the 404 case, cut down to 57mm, would be the perfect fit for any of millions of mausers out there, if ran at 55k or less pressure... and, of course, starting with a .358 bore and a 20" barrel

jeffe

Bwana-be:

In you modeling did you hold COL to 3.34 and let the longer bullets intrude on the powder space? The .358s will gobble up 10 grs of water capacity for every centemeter of intrusion.

I think you are quite close, as scaling up the 338 Dakota to 358 gives 4925 FPE with H4831at 65,000 PSI. Thats with a 250 gr 338 seating depth and intrusion, so the 280 gr 358 should give the same usable capacity, minus 1 gr for diameter, and 2810 fps.

Now THAT will work in Africa!!

The Dakota case is much better, you are right...

Sabot, to answer your question, I wasn't nearly that scientific. I just looked at the velocities from similar SD bullets in 338 and 375 calibers, and took into account that, generally speaking, a bigger caliber will go a bit faster than a smaller one in the same bullet weight. (E.g., a 375 Dakota may push a 270 gr 2900 fps, but the same bulelt weight in .358 caliber will be (my guess) 2875 fps.)
I have been accused before of ballistic optimism, but I've seen the Dakota data beat soundly, so I wouldn't be surprised to see my guess right in their with "reasonable" hot loads.

i was at the smiths yesterday and he showed me a 700 remington chambered in 358/378 weatherby. 24" tube with a brake. saw one of the rounds! holy crap!
guy shot it for the first time without a break. knocked his ass flat. looked very nice though.
woofer

this is a straight neck up of a 338 rum to 358 trimmed to 2.62"

www.z-hat.com has a 358 yukon...a shortened rum to fit in an 06 length gun.