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Old July 10, 2014, 09:58 PM   #1
thesheepdog
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338-300 Win Mag

Hello everyone,

Does anyone have on of these loadings?
I heard about this recently and can't get my mind off of it.

I have 338 barrel blank that I'm tempted to chamber on this caliber loaded to CIP length. And just so you know, I have a 338 Edge already...so spare me the comments that I should go with something else.

I like the idea of using 300 WM brass necked up to accept the long, high BC Berger 300gr bullets (loaded to 3.8ish")
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Old July 11, 2014, 08:12 PM   #2
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The short neck of the 300 Win mag case may not hold .338 bullets against the recoil of such a wildcat. Do you have something against the common 338 Win mag?
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Old July 11, 2014, 08:14 PM   #3
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What do you mean by recoil and the neck not holding the bullet?
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Old July 11, 2014, 10:52 PM   #4
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The .300 Win Mag already has a short neck compared to other calibers, I believe Mobuck is saying that expanding the already short neck to .338 may not give a long enough neck to provide the tension/friction to keep the bullet in place under recoil for cartridges in a magazine.
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Old July 11, 2014, 11:30 PM   #5
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Expanding the .300 Win Mag to take .338 bullets would make the neck longer, but not that much longer. If I correctly remember my high school trigonometry, the neck length would increase to .2874, when necking up to .338. I've always "heard" that necks should be at least one caliber to provide enough friction to keep the bullet from moving under recoil. I guess in this instance, that would be .330. As data points, the neck length of the .338 win mag is .331 and the neck length of the .338 ruger compact magnum is .320.

I don't know how hard and fast that rule is. The neck length of the .300 win mag is .264, which is well under .300. However, I've never had problems with bullets moving in my S&W 1500, .300 win mag. I almost always shot un-crimped 165 grain bullets. The few 180 grain bullets which I used, were crimped.

(@crankylove: Hello! Haven't seen you post for a while. Hope you're fine.)
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Old July 12, 2014, 07:06 AM   #6
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I'm not familiar with this cartridge. What do you expect to gain over just loading 338 WM?
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Old July 12, 2014, 08:29 AM   #7
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military snipers and target shooters shooting out past 1200 meters need the sectional denscity of a 300 grain spitzer to be stable in the wind.

but for hunting with modern bullet technology a 30 caliber 200 grain swift A frame hits harder and penitrates as well or better than a .338 using older bullets.even the 175 gr 7MM bullet is 1200 lb Bear worthy with good bullets and good handloading.

why not just use .300 magnum or a 7MM ultra magnum,why invent a new .338

i would like a .30-378 WB someday what can .338 do that it cant
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Old July 12, 2014, 08:37 AM   #8
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Quote:
Originally Posted by jmr40 View Post
I'm not familiar with this cartridge. What do you expect to gain over just loading 338 WM?
The 338 WM has a shorter case than the 300 WM. This equates to nearly 10gr difference in powder capacity. By using the 300 WM brass over the 338 WM Brass, I'm able to push the bullets a little faster.



Quote:
Originally Posted by green_MTman View Post
military snipers and target shooters shooting out past 1200 meters need the sectional denscity of a 300 grain spitzer to be stable in the wind.



but for hunting with modern bullet technology a 30 caliber 200 grain swift A frame hits harder and penitrates as well or better than a .338 using older bullets.even the 175 gr 7MM bullet is 1200 lb Bear worthy with good bullets and good handloading.



why not just use .300 magnum or a 7MM ultra magnum,why invent a new .338



i would like a .30-378 WB someday what can .338 do that it cant

I've heard the question "why?" often. Well, I already have a 338 Edge and I've got a spare barrel in 338. I wanted to chamber the third barrel in a 338 caliber that has readily available reloading components while also able to fit in a magnum bolt face.
The 338-300 WM fits the bill. Being as the military just adopted the XM2010 and ordered 3.8 million rounds of ammo for it, I figured that the 300 WM is going to become more and more available with the possibility of Lake City brass. I don't give a rats behind whether the case has a belt or not. I've got a 338 Edge.
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Old July 12, 2014, 09:30 AM   #9
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Quote:
I'm not familiar with this cartridge. What do you expect to gain over just loading 338 WM?

The 338 WM has a shorter case than the 300 WM. This equates to nearly 10gr difference in powder capacity. By using the 300 WM brass over the 338 WM Brass, I'm able to push the bullets a little faster.
Fair enough. Do you think the long 300 gr bullets combined with a longer case will cause problems with ammo being too long for the mag box?

Not being critical of your choice, just trying to learn.
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Old July 12, 2014, 09:33 AM   #10
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That's a good question. My setup won't have these issues. This is a purposes built rifle using a Mcree extended mag folding stock (uses AICS/accurate CIP 3.85" mags)
I'll have the bullets loaded to fit this mag box and the barrel throated for the extended length.
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Old July 12, 2014, 10:07 AM   #11
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@sheepdog: There is so much duplication of ballistics in the current cartridge line-up, that I suspect we could eliminate half of the commercial cartridges and still be served none the worse. But where's the fun in that? There is much enjoyment is loading and experimenting with uncommon cartridges, and so I say if you want a .338-300 win mag, then ignore the denigration and go for it.

When I first read your proposal, I wondered if you would lose the advantage of increased case capacity due to the short neck and the necessity of seating bullets so deeply. That's one of the problems I run into with heavier and longer bullets in my .300 win mag. However, maybe you will bypass that problem with a longer magazine and throat, as you have planned.

My only other observation is: wouldn't the recoil be brutal? My idea of a long range cartridge is one of the 6.5's or a .220 swift. Fewer loose dental fillings and detached retinas that way.
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Old July 12, 2014, 11:50 AM   #12
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@sheepdog

if you love it do it.

i did not need a 6.5-55 swedish mauser when i bought it,the 7MM-08 or .260 rem is more practical.l but the 6.5 swede so much more FUN
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Old July 12, 2014, 11:57 AM   #13
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Yeah I am really looking forward to this cartridge.
It should exceed the ballistics of a 300 WM loaded with 230 Bergers. And I won't have to fireform cases or anything weird like that. Just neck up and shoot.
That'll give me a very nice long range setup in the event brass is hard to come by for the Edge.
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Old July 12, 2014, 08:50 PM   #14
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It is commonly considered that the neck be at least one caliber long to properly hold bullets w/o requiring crimping.
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Old July 12, 2014, 10:14 PM   #15
thesheepdog
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Quote:
Originally Posted by Mobuck View Post
It is commonly considered that the neck be at least one caliber long to properly hold bullets w/o requiring crimping.

A common consideration, yes but the 300 WM, 338 RUM and others don't follow this rule.
I'm not worried about it.
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Old July 13, 2014, 11:48 AM   #16
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If you can really get an extra 10 gr of capacity it might be worth it from a ballistics standpoint. These are just "back of the napkin" guestimates, so use anything here at your own risk, I make no claims for safety or performance.

A 338 Win Mag with a max charge of IMR4350 listed by Hodgdon nets 2,420 fps at 64gr compressed. That works out to 37.4 fps/gr.

The 338 Win Mag has 86gr case capacity. 64gr IMR4350/86gr H2O = 74% fill rate. An additional 10gr of H2O capacity for you wildcat times 74% gives 7.4gr more IMR4350 to compressed. So an additional 7.4gr of powder would be 71.4gr, 71.4gr times 37.4 fps/gr = 2,670fps max charge with IMR4350, from a 24" barrel.

Food for thought anyways.

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Old July 13, 2014, 12:21 PM   #17
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It would be the 10gr increase (give or take) plus the long throat.
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Old July 14, 2014, 07:34 AM   #18
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thesheepdog, Kind of funny but I'm shooting 30x338mag got two of them.
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Old July 14, 2014, 07:47 AM   #19
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The 30-338 is cool. Longer neck than the 300 WM but you lose case capacity over the 300.
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Old July 14, 2014, 07:56 AM   #20
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I'm all for the custom stuff

how much actual difference is there between the 8mm Magnum & the 338-300 ???

hmmm. thought there would be heavier 8mm bullets, but looks like 220 grain is about the heaviest of anything with a decent ballistic coefficient...

maybe 338 - 8mm mag
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Old July 14, 2014, 02:43 PM   #21
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If I understand the OP right part of the motivation is to get increased performance, with readily available brass. 300 WM is certainly one of the more readily available magnum cases. Much more so than 8mm, which might be better performance wise.

I dabbled with 338-06 for a while. I chose it for the same reasons, brass is easily made from 30-06 brass and I just liked it better than 35 Whelen.
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Old July 15, 2014, 08:07 AM   #22
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thesheepdog, I've had 2 300WSM, 2 300 mags build also couple 300Wby beside the 30x338mag. I have fair amount of reloading data for all and it's all in how you have them build. I gave my nephew 300WSM and 300mag so still in the family. Like you my rifles are not open to a debate.
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Old July 25, 2014, 05:42 AM   #23
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I've thought about a 338-06 lately, but I already have a .338 WinMag and can't get myself to pull the trigger on the 338-06. It has less recoil than my WinMag, but the WinMag has a lot more horse power and is easy to find when away from home and I run out of shells. It can also be loaded down for medium sized game, or bumped up for dangerous game. Don't see much 338-06 on the shelf in podunk Montana, or anywhere West Texas.

A 338-300 WM sounds neat, but why it over a 300 WM, or a .338 WinMag for that matter? Just curious.
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Old July 25, 2014, 06:27 AM   #24
jmr40
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Quote:
A 338-300 WM sounds neat, but why it over a 300 WM, or a .338 WinMag for that matter? Just curious.
I asked the question earlier, his reply in post #8

Quote:
The 338 WM has a shorter case than the 300 WM. This equates to nearly 10gr difference in powder capacity. By using the 300 WM brass over the 338 WM Brass, I'm able to push the bullets a little faster.
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Old July 25, 2014, 07:45 AM   #25
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If you want more performance over a .338 WM and readily available brass do a .338 Campfire. It's also known as a .338-375 Ruger. The Ruger case has nearly 100 grains of H2O capacity and that puts you in .340 Weatherby territory and only 13 grains behind the .338 RUM.

I know if I was going to do a magnum wildcat I'd get rid of the belt on the case.
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