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10-04-2021, 13:29 #11
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Re: .338 Imperial Magnum Chassis fun project
As I see it the only other option to be able to get a great platform for the type of project we are discussing here is to use the .416 Rigby case as a long range rifle . But then you are looking at expensive brass , much heavier recoil, although that can be dealt with in using the correct chassis with adjustable counter weights fit onto the chassis as is my plan to do.
This will be a great platform like the .505 Gibbs used by the CheyTac company..
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10-04-2021, 14:06 #12
Re: .338 Imperial Magnum Chassis fun project
The parent case for EDGE / RUM is not Jeffery, even if Wikipedia says so. 338 Edge is 300 RUM necked up with no changes. 404 Jeffery is not a rebated rim. Bolt face sizes and other key dimensions differ. Just measure the brass and see.
Nobody ever chambered a RUM from 404 Jeffery brass, the commentators mean the dimensions are similar to a 404 Jeffery. Same for the new Nosler cartridges.
In your case, the 338 Imperial is actual 404 Jeffery brass, necked down, running at 338 Lapua + pressure, which I suggest you look into more carefully.
.416 Weatherby is the correct pressure rating, in an action rated for 338 Lapua. With 140 grains case capacity, in a 36 inch barrel, you can get to within 100 fps of 408 Cheytac velocity with a 20 grains lighter bullet. Mojet type 3 action, 12 twist barrel throated long, and off you go.
Cheytac based their cartridge on Gibbs dimensions. Cheytac themselves warn not to resize Gibbs brass for their calibers.
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10-04-2021, 15:00 #13
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Re: .338 Imperial Magnum Chassis fun project
414 Gates, let me qualify it better:
The Imperial Magnum is the first non belted magnum based directly on a 404 Jeffery/10.75 x 73 case without making changes to the case itself..while the RUM and WSM and other cases similar as the 404 Jeffery case ( they all are based on the 404 Jeffery case concept..
They, RUM/WSM from Remminton /Winchester company altered the 404 Jeffery case at the base and blow it out..
if you place the 404 Jeffery /10.75 x 73 Shuler along side these cases you will see a remarkable resemblance ...good, so there will be changes affected to the original 404 Jeffery/10.75 x 73 case design , but in essence they are the same kettle of fish..if the RUM cases was all belted magnums I would accepted that it was a different case ...I see them as part and parcel of the 404 Jeffery case.As not to be splitting a hair now
My focus in this thread being the milling of a chassis as a long range platform for fun shooting ..not per sae the 404 Jeffery case design..still the .338 Imperial Magnum has a great history around it and this is one reason why I focus on the 404 Jeffery/10.75 x 73 S caliber to build these two scarce caliber rifles on it..and I perceive the 404 Jeffery/10.75 x 73 S as the perfect designed case and caliber of all time..the .375 H&H Magnum being second to it...
414 Gates , why do you think HOWA action and .338 barrel will not be able to handle the .338 Imperial Magnum round???
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10-04-2021, 15:26 #14
Re: .338 Imperial Magnum Chassis fun project
I'm not sure that Howa build actions for 60,000 + psi pressure, which is what the 338 Imperial produces according to the load data.
As I said before, you may intend this to emulate 338 Win Mag performace, which the Howa action has no problem with, just stamp somewhere on the rifle the max psi you build it for.
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10-04-2021, 15:36 #15
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Re: .338 Imperial Magnum Chassis fun project
The .338 Win Mag psi is 64000psi
I will contact the HOWA company in Japan and ask about their pressure tests on their .338 caliber actions. 414 Gates , I never sell a rifle if I paid for it...this rifle will be mine until end of days
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10-04-2021, 19:49 #16
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Re: .338 Imperial Magnum Chassis fun project
Good, I will be focusing on the butt stock first, getting a 400 x 200 x 40 mm high grate aluminum heavy sheet metal to duplicate and make changes to the example I want to duplicate as well as incorporate features into it that I like... I will purchase this piece of high grade aluminum to work on the design .
First I need to make an exact pattern of the example .
With some time I will work on what I want from the original item and my own preferences into the design.
A great feature of this chassis I am using as a base platform to design my chassis is that this is the first ever chassis I found the past seven years that has a feature of adding weights in to the frame of the chassis to negate /dissipate hard felt recoil..it is just a really inventive feature for sure..first of it` kind..I will be incorporating this great feature into my chassis build as well.. Members, clicking on the photo/thumbnail will enlarge the photo for you to have a close up look at it.
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10-04-2021, 22:31 #17
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Re: .338 Imperial Magnum Chassis fun project
I got an interesting reply from the originator of the .338 Imperial Magnum. This is in regards to re-loading data .
.338 Remington Ultra Magnum = 65000 psi
.338 Winchester Magnum = 64000 psi
.338 Lapua Magnum
60916 psi
.338 Norma Magnum
63817 psi
Keep in mind the Lapua and Norma are .416 Rigby cases
.338-378 Weatherby Magnum 63817 psi
Gert; Because Remington copied and duplicated my .338 you can use any reloading manual that has the .338 Ultra Mag listed and use that data as a reference for the .338 Imperial Magnum – they are exactly the same.
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11-04-2021, 08:55 #18
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Re: .338 Imperial Magnum Chassis fun project
Looking at .416 Rigby case capacity :
404 Jeffery : 7.32 cm3 (113.0 gr H2O)Case capacity 7.532 cm3 (116.24 gr H2O)
Not much differences , wondering about what best powder to use with these flat shooting calibers. What makes it more an optimal shooting platform is the probability to make use of the powders used by shooters in the USA and other countries who already supply powder to South African shops.
It opens up a great opportunity to re-load according to their specs and not to SONCHEM powders anymore. If possible I would not want to use SONCHEM powders at all.
I would like to hear from members in regards to this statement and if there are already members not using SONCHEM powders at all for their reloading .
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11-04-2021, 09:07 #19
Re: .338 Imperial Magnum Chassis fun project
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11-04-2021, 11:52 #20
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Re: .338 Imperial Magnum Chassis fun project
414Gates, thank you I really enjoy your participation in regards to what I want to do building a fun shooting long range rifle in the scarce .338 Imperial Magnum on a aluminum chassis.
Do your company sell the USA/Sweden/ companies' rifle powders?
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