375 RUM Build

Whitetail312

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Jun 15, 2018
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Loganville, GA
Does anyone here shoot one? I was originally thinking of doing a CheyTac build but I already have a 700 donor long action in the safe I could use I believe. Or am I wrong and the bolt face won’t work? It’s a 7mm mag action originally. But if the action will work, are any of you here using one? I’m thinking a 28-30” barrel shooting a 300 grain burly should get me way out there with a ton of energy, for much less cost than a cheytac build. Any help and or opinions are very welcome.
 

Overkill338

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Sep 23, 2008
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Virginia
The bolt face on a 7 mag is the same as the RUMs. All use a 0.532" shell holder on the press. I believe Remingtons long action rifles are all magnum length too. It's been a long time so dont quote me. I'll be interested I'm seeing where this goes. The .375 RUM is one I'd love to shoot.....at least once!
 

Overkill338

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Yes it is, that’s why I’m wondering if the action is strong enough for this cartridge
Yes, all the long actions are the same.

Max pressure on a 375 RUM is 65k psi. A 7mm Rem Mag is around 63k. Not much difference. 300 Win Mag is 64k, and all use the same action. Obviously it wouldn't hurt to have a Smith check it over good. That's about all I can add.
 

sable tireur

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Yes, all the long actions are the same.
While the bolt face is the same diameter as the standard belted magnum cartridges, the body diameters are different with the RUM body being decidedly larger in diameter. The Remington M700 action will handle the RUM cartridge (Remington Ultra Magnum), it's important to pay attention to the width of the opening in between the action rails. Action rails are cut to allow the cartridge to feed from the box by the follower up into the feed ramp. But there has to be enough material left to hold the remaining cartridges down. You may need to adjust the feed ramp as well.

.375 RUM
upload_2019-6-24_14-32-16.png


The RUM cartridges, like the WSM cartridges, require the magazine box with the triangular windows cut into them. Getting some cartridges to feed reliably is both skill and art.


From left to right: .376 Steyr, .375 Flanged Magnum, .375 H&H, .375 Ruger, .375 Weatherby Magnum, .375 Remington Ultra Magnum, .378 Weatherby Magnum.
 
Last edited:

Whitetail312

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Jun 15, 2018
Messages
111
Location
Loganville, GA
So it seems it’s doable I believe. I can’t find any bottom metal for the 375, would a 338 bottom metal work since they’re both the same parent case?
 

Rum Man

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Nov 2, 2017
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Montana
I single feed my 3 338 Edges so Bdl bottom metal works for me . They are around 3.90 oal

Rum Man
 

Overkill338

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Joined
Sep 23, 2008
Messages
1,172
Location
Virginia
While the bolt face is the same diameter as the standard belted magnum cartridges, the body diameters are different with the RUM body being decidedly larger in diameter. The Remington M700 action will handle the RUM cartridge (Remington Ultra Magnum), it's important to pay attention to the width of the opening in between the action rails. Action rails are cut to allow the cartridge to feed from the box by the follower up into the feed ramp. But there has to be enough material left to hold the remaining cartridges down. You may need to adjust the feed ramp as well.

.375 RUM
View attachment 138992

The RUM cartridges, like the WSM cartridges, require the magazine box with the triangular windows cut into them. Getting some cartridges to feed reliably is both skill and art.


From left to right: .376 Steyr, .375 Flanged Magnum, .375 H&H, .375 Ruger, .375 Weatherby Magnum, .375 Remington Ultra Magnum, .378 Weatherby Magnum.
I said don't quote me lol
 

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