Building a 358 ultramag

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David L

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I'm wondering: necking down a 375 or necking up a 300? would that change the reamer needed? I have access to 375 with no problem so I was thinking of doing that. I want an OAL the same as 375 or 300 not like 338 rum wich is a bit shorter. What do you think? I'm planning of doing a hunting rifle, portable.24 or 26 inches?
Thanks
 
I am assuming the purpose of such a large case is you want maximum velocity. To achieve maximum velocity will require all the barrel length you can give it. For that reason go long, 26 as a minimum. There are better cartridges for shorter barrels.
 
I have a custom built 375 ultra mag I'm running a 28.5" barrel on it. It will push 250gr gmx's at 3100fps. That gun will level a moose or elk really quick. I think the 35cal would be fun too just not as much of a bullet selection.
 
Well it seems to be evolving that a 375 is way too small for hunting in North America... shortly a 458 Lott will be the minimum that can kill anything larger than a deer.
 
mudpro said:
...I think the 35cal would be fun too just not as much of a bullet selection.
Click to expand...

180, 200, 220, 225, 250, 275, and 310gr 35 caliber bullets available for my 350 Remington Magnum, as well as 38 caliber pistol bullets for plinking.
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I have one I had it built to use the 300 RUM case, the 357 RUM is slightly shorter so you may need different reamers. Don't know for sure.
 
My old sheep hunting partner had one for many, many years, long before the Imperial Magnum or Remington came out with the RUM line up. It was then known as the 35-404 Imp 30*.........outstanding cartridge but don't use C+C bullets, it literally tears them to itty bitty pieces on impact with anything. It rivals the 378 Wby for energy and recoil and kills everything it touches right out to 500+ mtrs. His rifle was built by Bevan King on a P14 action (IIRC) with a 26" barrel of his own making. It is a fire breathing, killing machine if you're up to the recoil and it shoots very well with most bullets. My buddy finally found some Swift A-frames in 250 gns to hunt with and used 250 gn Speer HC for varmints and plinking. It is a major step up from the 358 NM or the 358 STA. With no load data to go by he worked up a load with 250s at a touch over 3300 fps. His 404 brass was still happy and keeping primer pockets tight so this was the load he used, it also shot about 3/4 moa very consistently with both the Speers and the A-frames.
 
I have a 358 sta and it is awesome, but I found that brass was getting harder to find and didn't last long. So I built a 35-338 lapua improved now I don't worry about brass anymore.
 
Slamfire said:
180, 200, 220, 225, 250, 275, and 310gr 35 caliber bullets available for my 350 Remington Magnum, as well as 38 caliber pistol bullets for plinking.
tu.gif
Click to expand...

Should have said that differently there is a selection of bullets. Been hard to find much of a selection in the gun shops that are anywhere around me anyways. And getting bullets shipped is never cheap it seems.
 
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