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Thread: 7mm mag to 358 Norma

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    Default 7mm mag to 358 Norma

    Guys, I'm kind of an ignoramous when it comes to the big thumpers that you are accustomed to. I have a real nice Ruger 77 in 7mm mag that I just picked up for very little jingle. I'm bettin that JES could rebore that rifle to 358 without much effort. My question is that all a 358 Norma is? Just a standard magnum that was derived from the H&H case necked to 358 as in a 7mm mag necked up?

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    Quote Originally Posted by elmerkeithclone View Post
    Guys, I'm kind of an ignoramous when it comes to the big thumpers that you are accustomed to. I have a real nice Ruger 77 in 7mm mag that I just picked up for very little jingle. I'm bettin that JES could rebore that rifle to 358 without much effort. My question is that all a 358 Norma is? Just a standard magnum that was derived from the H&H case necked to 358 as in a 7mm mag necked up?
    Interesting thought here EKC! I also have a Ruger 77 in 7mm mag sitting here that I have been working on fitting a stock for. I admittedly have grown uninspired with the project since it just doesn't fill any need in my arsenal. I don't currently have a thumper though and it would be kind of cool to hack this one back to 20-22" and blow it out to at least 358... I am very curious to see what you find out on this!!

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    Hey how are things up your way. I haven't had time to get on this site much lately and haven't had the chance to disrupt normal thinking as I usually do. It's good to see you in print again.

    The 358 Norma mag contrary to what most believe is not derived from any of the American belted mags. The 458 Win, the 338 Win, 264 Win and the 7mm Rem mag are from the same case, same mould. Particularly the 7 mag and 338 Win are identical except for neck diameter. A key measurement is from the case head to the start of the shoulder. The 7mm and 338 are 2.040 inches. This dimension becomes the headspace dimension if you want to load cases correctly and not loose them to the belted case stretch. The 358 Norma dimension to the shoulder 2.084 inches. That is .044" of excess headspace that would result in case stretch at first firing if you used 7 mag or 338 Win brass. Of course the cases technically headspace on the belt but if the shoulder of the case is .044" back from the chamber shoulder the case will stretch to fill that void. Case separation will be the result on some subsequent firing.

    You would need to send a finish reamer down the chamber to be able to load factory 358 Norma ammo (and have it stamped 358 Norma). Otherwise you will have a wildcat, 7mm/358. The max case length of the 7mm and 338 is 2.500" the Norma is 2.520" Overall length is close at is 3.340" for the 7mm and 338 and the the Norma is 3.346" All other dims are so close as to offer no difficulty. If you run a reamer into the chamber and rebore and cut to .350"/358" respectively you'll have a 358 Norma mag.

    I hope this helps, good luck with the project.
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    Ya know, since you're reaming the chamber anyway, maybe you should consider something on the Ruger case in .358" caliber. No belt and its difficulties. Same length and lots of brass available now.
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    Quote Originally Posted by Murphy View Post
    Ya know, since you're reaming the chamber anyway, maybe you should consider something on the Ruger case in .358" caliber. No belt and its difficulties. Same length and lots of brass available now.
    Would this be an easy way to hit the 358 Nukalpiaq. What is the status on that cartridge now regarding dies and brass? I recall there was work on a forming die that could get you ready to run factory brass without fire forming but may well be mistaken.

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    If you go the 358N, brass can easily be made from 300Win and there is no head space issue.

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    Quote Originally Posted by Murphy View Post
    Ya know, since you're reaming the chamber anyway, maybe you should consider something on the Ruger case in .358" caliber. No belt and its difficulties. Same length and lots of brass available now.
    Good to hear from you Murphy and as always you have answered my question to the "T". Initially I had thought about sending this rifle back to Ruger and just having it rebarreled to 375 Ruger. However they answered my email with a big fat no. Ruger has always been my favorite layperson priced rifle, but I don't do well with attitudes and even though I have been loyal to them they could care less. I mean they make the rifle in their factory to start with how hard could it be to unscrew one barrel and screw on another one. They used to do it for cheap as I had one particular 243 rebarreled twice.

    Brownells is just a coffee break away and I'm thinking that they could fix me up with the Norma mag reamer. I think I'll talk to them.

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    Quote Originally Posted by elmerkeithclone View Post
    Guys, I'm kind of an ignoramous when it comes to the big thumpers that you are accustomed to. I have a real nice Ruger 77 in 7mm mag that I just picked up for very little jingle. I'm bettin that JES could rebore that rifle to 358 without much effort. My question is that all a 358 Norma is? Just a standard magnum that was derived from the H&H case necked to 358 as in a 7mm mag necked up?
    EKC, this is basically how I got my .358 Norma, although I started with a new barrel because my 7mm Mag was too light a contour for my taste. Mine was built on a commercial Mauser, but the 77 would make a dandy rifle as well. You can rent the reamer from 4-d Reamers for about $35 bucks, but I think JES has the reamer so you wouldn't need one. Jesse will fix you right up.

    The .358 Norma is truly my favorite cartridge. There's nothing it can't be loaded to do.

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    Quote Originally Posted by Murphy View Post
    The 358 Norma mag contrary to what most believe is not derived from any of the American belted mags. The 458 Win, the 338 Win, 264 Win and the 7mm Rem mag are from the same case, same mould. Particularly the 7 mag and 338 Win are identical except for neck diameter. A key measurement is from the case head to the start of the shoulder. The 7mm and 338 are 2.040 inches. This dimension becomes the headspace dimension if you want to load cases correctly and not loose them to the belted case stretch. The 358 Norma dimension to the shoulder 2.084 inches. That is .044" of excess headspace that would result in case stretch at first firing if you used 7 mag or 338 Win brass. Of course the cases technically headspace on the belt but if the shoulder of the case is .044" back from the chamber shoulder the case will stretch to fill that void. Case separation will be the result on some subsequent firing.

    I hope this helps, good luck with the project.
    I've never experienced resizing 338 WM to 358 NM causing any kind of issue. The neck ends up a bit shorter than spec'd for the Norma cartridge and the shoulder is pushed forward, but since the cartridge does/can headspace on the belt I've not encountered case separation issues with subsequent firings, but I admit after the fire forming I headspace on the shoulder not the belt. I'm not being argumentitive, just that IME virgin .338 WM cases make perfectly viable .358 NM cases once they are sized and fire formed. Admittedly, my experience with the Norma round is limited to one rifle, but I've talked to others and read numerous reports of shooters forming .358 Norma cases from .338 WM without a hiccup. I've also read that some shooters form the .358 Norma by using .300 WM cases thereby creating a false shoulder to prevent the effect you're describing while also providing a longer neck than either the 7mm RM or .338 WM, but that seems to be a lot of effort (extra trimming and more difficult resizing) for an issue that isn't really an issue.

    In a similar vein, I've used .375 H&H cases to form .340 Weatherby cases and never suffered a case separation as a result. In that "conversion" the fire forming process moves a lot of brass through the shoulder and case body. I think that procedure is moving more brass than in the .338 to .358 conversion.

    To the best of my knowledge, the only separations I've experienced (.243 Winchester & 25/06) have come as a result of over zealous resizing, with regard to chamber dimensions, and repeated use. Otherwise I've sized virgin brass up and down depending on what is available and what I need with nary an issue.
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    Quote Originally Posted by evandailey View Post
    EKC, this is basically how I got my .358 Norma, although I started with a new barrel because my 7mm Mag was too light a contour for my taste. Mine was built on a commercial Mauser, but the 77 would make a dandy rifle as well. You can rent the reamer from 4-d Reamers for about $35 bucks, but I think JES has the reamer so you wouldn't need one. Jesse will fix you right up.

    The .358 Norma is truly my favorite cartridge. There's nothing it can't be loaded to do.
    Thanks Evan! I have 100% faith in Jess's abilities. That is what I'm going to do. He has rebored 7 or eight rifles for me and I was thrilled with every one. I have never had him ream a chamber but if wants the work then he's got it. What barrel length is your Norma Mag? I will use my 338-06 with 215 grain bullets as my middle bore thus this 358 will be my big gun so 250 grain would be the smallest bullet that I'm likely to use so I'm thinking 20 -22 inches.



    Now back to some brain wandering on my part. Murphy suppose I was to have the rifle rebored to .358 but left the chamber alone. Why could I not just resize some 338 WM brass in a 338 WM die and then just neck size them in my 350 Rem mag dies. Then on subsequent reloading just neck size the brass and leave the rest of the case fireformed to my chamber again using the 350 Rem mag dies? The shoulder angle on both the 338 WM and the 350 Rem Mag are both 30 degrees. Would this be possible?

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    Quote Originally Posted by elmerkeithclone View Post
    Thanks Evan! I have 100% faith in Jess's abilities. That is what I'm going to do. He has rebored 7 or eight rifles for me and I was thrilled with every one. I have never had him ream a chamber but if wants the work then he's got it. What barrel length is your Norma Mag? I will use my 338-06 with 215 grain bullets as my middle bore thus this 358 will be my big gun so 250 grain would be the smallest bullet that I'm likely to use so I'm thinking 20 -22 inches.



    Now back to some brain wandering on my part. Murphy suppose I was to have the rifle rebored to .358 but left the chamber alone. Why could I not just resize some 338 WM brass in a 338 WM die and then just neck size them in my 350 Rem mag dies. Then on subsequent reloading just neck size the brass and leave the rest of the case fireformed to my chamber again using the 350 Rem mag dies? The shoulder angle on both the 338 WM and the 350 Rem Mag are both 30 degrees. Would this be possible?
    My barrel is 22" 1-14 Twist. I've not felt I gave up any velocity worth noting at that length. I've had good success with Nosler 225's and Hornady 250 RN's. I haven't tried many others.

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    EKC:

    I'm glad to have you among us again, even just for fleeting moments.

    I looked into rebarreling my Rem. 700 7mm RM to a 358 Norma one time ago, although I didn't do it.

    This is only as accurate as my memory, but I understand your best bet is to reform 300 WM cases to make brass for the 358 Norma.

    The necks will end up longer, and you must trim them, BUT if you don't wanna do that, you can just have the 358 Norma chamber neck made longer.

    358 Norma rounds would still work fine with their SHORTER necks so no problem there. Besides a longer neck is a good thing.

    I resize 7mm RM brass in a 7mm Weatherby sizing die to use in my 7mm Weatherby. The necks end up shorter, but it's notta problem.

    Doesn't that 7mm Rem. Mag. thump you enough? Or thump those coyotees enough?

    It's a great cartridge, FAR SUPERIOR to a 270 or 243.

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    Quote Originally Posted by Smitty of the North View Post
    EKC:

    I'm glad to have you among us again, even just for fleeting moments.

    I looked into rebarreling my Rem. 700 7mm RM to a 358 Norma one time ago, although I didn't do it.

    This is only as accurate as my memory, but I understand your best bet is to reform 300 WM cases to make brass for the 358 Norma.

    The necks will end up longer, and you must trim them, BUT if you don't wanna do that, you can just have the 358 Norma chamber neck made longer.

    358 Norma rounds would still work fine with their SHORTER necks so no problem there. Besides a longer neck is a good thing.

    I resize 7mm RM brass in a 7mm Weatherby sizing die to use in my 7mm Weatherby. The necks end up shorter, but it's notta problem.

    Doesn't that 7mm Rem. Mag. thump you enough? Or thump those coyotees enough?

    It's a great cartridge, FAR SUPERIOR to a 270 or 243.

    Smitty of the North
    One particular winter the mange took over the coyotee herd in the northwestern part of our hunting range. We were shooting them and then draggin them to the nearest ditch. I actually shot a couple of yotes with the 7mm mag that winter. When you load that case full of 4831 and stick a itty bitty cheap 120 grain boolit on top it almost cuts a coyotee in half......kinda cool! One fella in the group used a 358 Norma some that winter and he loaded pistol bullets for coyotes. He did a Texas heart shot on one coyotee and it looked like it stepped on a bomb. I normally don't think it's ok to blow em up but the mange turns the hunt into a mercy killing so in such times it's ok to take drastic measures.

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    I think I would just order some new brass to get the new gun rolling along and be done with it EKC, I can't imagine you are ever going to shoot that puppy enough to warrent all the effort to custom size a batch up?
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    Quote Originally Posted by LuJon View Post
    Would this be an easy way to hit the 358 Nukalpiaq. What is the status on that cartridge now regarding dies and brass? I recall there was work on a forming die that could get you ready to run factory brass without fire forming but may well be mistaken.
    The cartridge is alive and well, albeit in small quantities, but there are a few happy owners. It has about 5 grains more capacity than the 358 Norma. A recent convert was a Krieger barreled Sako AV action. I have one more set of dies and about 100 rounds of formed brass. The brass from basic cylindrical, no head-stamp.
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    Quote Originally Posted by elmerkeithclone View Post

    Now back to some brain wandering on my part. Murphy suppose I was to have the rifle rebored to .358 but left the chamber alone. Why could I not just resize some 338 WM brass in a 338 WM die and then just neck size them in my 350 Rem mag dies. Then on subsequent reloading just neck size the brass and leave the rest of the case fireformed to my chamber again using the 350 Rem mag dies? The shoulder angle on both the 338 WM and the 350 Rem Mag are both 30 degrees. Would this be possible?
    Yes that would work fine. The shoulder angle on both are 25 degrees I believe and the 350 is a cut 338 WM case which leaves its shoulder diameter slightly larger than the 338 shoulder. (.495" vs .491") but it will work and you wouldn't need a new set of dies. That sounds like the budget way to go. But the rifle is now something other than a 7mm Mag and I believe it is required to be stamp as to the caliber/cartridge it shoots. A 358 EKC?
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    Well, you couldn't just leave the chamber alone, could you?

    The chamber includes the neck which would hafta be larger and be right ????

    Smitty of the North
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    Quote Originally Posted by 1Cor15:19 View Post
    I've never experienced resizing 338 WM to 358 NM causing any kind of issue. The neck ends up a bit shorter than spec'd for the Norma cartridge and the shoulder is pushed forward, but since the cartridge does/can headspace on the belt I've not encountered case separation issues with subsequent firings, but I admit after the fire forming I headspace on the shoulder not the belt. I'm not being argumentitive, just that IME virgin .338 WM cases make perfectly viable .358 NM cases once they are sized and fire formed. Admittedly, my experience with the Norma round is limited to one rifle, but I've talked to others and read numerous reports of shooters forming .358 Norma cases from .338 WM without a hiccup. I've also read that some shooters form the .358 Norma by using .300 WM cases thereby creating a false shoulder to prevent the effect you're describing while also providing a longer neck than either the 7mm RM or .338 WM, but that seems to be a lot of effort (extra trimming and more difficult resizing) for an issue that isn't really an issue.

    In a similar vein, I've used .375 H&H cases to form .340 Weatherby cases and never suffered a case separation as a result. In that "conversion" the fire forming process moves a lot of brass through the shoulder and case body. I think that procedure is moving more brass than in the .338 to .358 conversion.

    To the best of my knowledge, the only separations I've experienced (.243 Winchester & 25/06) have come as a result of over zealous resizing, with regard to chamber dimensions, and repeated use. Otherwise I've sized virgin brass up and down depending on what is available and what I need with nary an issue.
    To each his own methods. But if we're over zealous with the non belted we could be with belted. Why not adhere to the cartridge dimensions from the start?
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    Quote Originally Posted by Smitty of the North View Post
    Well, you couldn't just leave the chamber alone, could you?

    The chamber includes the neck which would hafta be larger and be right ????

    Smitty of the North
    Good point. Yes that sounds important. I would think that rebore would only bore and rifle where previously it was 7mm. So you would need a throating reamer(?) I don't know how that would work. What do we do when we reborn a 30-30 to 35 caliber (35-30)?
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    I have an old set of RCBS dies marked 338/358 so I'm sure it's been done before. It's not a Star Trek adventure. But I'd say it would require some chamber dimensional alterations. Throat and leade would need to be established for bullet of choice.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



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