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Thread: 300WM to 358 Norma

  1. #1

    Default 300WM to 358 Norma

    I have been trying a few things looking be able to use some less expensive brass for a 358 Norma I hope to sport soon.
    Found an old 300WM case and started taking a real hard look at the budget? ($35) Jax dies I got off of flee-bay. The expander had a real short taper to it so I figure that it was made to just resize factory fodder.

    Started looking at the new RCBS Whelen die and thought its expander was a bit more tapered and might work to resize 30 cal. brass. Seemed to screw in fine so there I was a couple of minutes later with real fine looking 358 Norma Mag. brass.

    Now, because I used 300WM brass it will be .100" or so too long so I will have to do a little trimming.

    I used my Whelen die to resize a few 30-06 shells and it seemed to work pretty good. Only one had a little split in it--a good one for OAL checking (NOT to used for a live round).

    I have read some information indicating that using 338WM brass can result in the shoulder being a little short of the full Norma length. I hear these will fire form nicely but I was hoping to get a little closer on the initial sizing so as to be able to use the cartridges in load development without having to first fire form them. Pushing the shoulder back and trimming the neck a little seems like the way to go.

    Am I on the right track or am I missing something?
    I do not have very much experience with this sort of thing and don't want to compromise safety for the price of a bag of brass.

    I was also wondering if sizing from 30 to 35 cal was too big a jump for a single pass.

  2. #2
    Join Date
    Apr 2006
    SwampView AK, Overlooking Mt. Mckinley and Points Beyond.


    I've always had some interest in a 358 Norma, and this is what I heard about on another forum, a while back.

    You make your 358 Norma brass by reforming the 300 Winchester brass, and the neck will then be too long, so have the neck in your chamber made longer to match. The longer neck is better, and you still have the option of using the regular 358 Norma cases too.

    Smitty of the North
    Walk Slow, and Drink a Lotta Water.
    Has it ever occurred to you, that Nothing ever occurs to God? Adrien Rodgers.
    You can't out-give God.

  3. #3


    I just built my first 358 Norma back in the fall and it was also my first endeavor at reloading on my own.

    My initial cases were in fact 338 Win Mag cases necked up to 358 and though the neck is a bit short it did not seem to affect accuracy in the least. In fact they shot a .75" 5 shot group at 100yds and that was before they had been fire formed and loaded again. Groups were the same after fire forming.

    By necking up the 300 Win Mag you are basically creating a wildcat called the 358 Epstein. Which is really just the 358 Norma with a longer neck. Like Smitty said you could just have your chamber cut a little longer and use either if that is what you're interested in.

    Ultimately for me it came down to the fact that I don't like the headstamp on my brass to be wrong. Just for safety I guess and the fact that if I ever leave the country with it it will have to have correct brass. So I was patient and watched the auction sites and was able to find 200 Norma new cases for a good price. Perhaps not as cheap as 300 or 338 WM but worth it to me. Now I should be supplied for a long time.

    Either way you go the 358 Norma is about the most versatile round I have ever messed with. I love it!

  4. #4

    Default 358 Norma

    I've used the 358 Norma for better than 20 years. Great cartridge. I use 338 WM brass. It's tough as nails and expanding the neck is a piece of cake. It has been my experience that Norma brass is soft and won't take near the pressure of the Winchester cases. I load my Norma right to the hips with H 4895 and a 225 gr. Nosler or TSX. Velocity runs about 2950 out of a 23" Douglas bbl. Very accurate. The 358 Norma is the all-time sleeper.
    Good luck with yours, you won't regret doing it.

  5. #5
    Join Date
    Aug 2007


    I am using 300WinMag brass for my 358Norma and as my neck area is a little long it allows me to leave the necks about .050 longer than normal. Nice long necks and cheap good brass. 250gr @2880 with IMR4350. Wrong headstamp doesn't bother me as they won't fit in anything else I have and I can't afford to hunt in any other country. Still wonder why US gun makers didn't chamber for this one. What a shame.

  6. #6

    Default factory brass

    My midway order arrived with a few Norma cases in it.
    The distance from the base to the beginning of the shoulder is quite a bit longer. I expect that a 358-300WM chamber would be a nice combo but the lack of a caliber (length) of neck is what would deter me.

  7. #7


    Which case are you saying would deter you? Factory 358 Norma cases do not have a caliber length of neck and the 300 mag cases necked up actually end up with a longer neck than .358 if I am not mistaken. I didn't understand what you were getting at.

    By the way, I mistakenly called the 358/300 WM the 358 Epstein in my earlier post. I was getting it confused with the 375/300 which is the "375 Epstein".

  8. #8


    I have had a 35-300 Win for 30 years on a Win 1917. No real trick to forming just run the .300 brass thru a RCBS 35-300 die. Slowly at first forming to avoid collapsing the shoulder.


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