I would like any information anyone can give me about a rechamber,and anything else I would need to do to make this conversion.I heard RIP knows his way around this job.Any and all help is appreciated. Thanks

quote:

Originally posted by longshots:
I would like any information anyone can give me about a rechamber,and anything else I would need to do to make this conversion.I heard RIP knows his way around this job.Any and all help is appreciated. Thanks

I added a few comments over on your other thread on the gunsmithing forum. It is a great conversion. Maybe not Kosher to Mike375, but I like it.

It is a big GO if you want a .378 Weatherby, which is "The Magnum's Magnum" according to dear departed Bob Hagel, who was a Magnum Man in the rifle whomp category.

Gotta go get ready to shoot the North Fork of the Platte .423/340gr sheep bullets at 2700 fps tomorrow.

Cheers

The RUM is a better choice if you have a 375 H&H, as the bolt face and feed ramp do not need to be modified. The 378 is a fine round, but it burns quite a bit more powder and has more recoil than the 375 RUM...all this for 100 fps.

If you handload, the RUM is far better with reduced loads and Hornady 225s can be launched as slow as 2700 fps with good accuracy for game that won't bite back.

I have done both the .375 RUM and the .378 Weatherby on a CZ 550 Magnum action.

You can rechamber a .375 H&H to do both. After opening up the boltface for the .378 and minor rail work, it was easy to get it feeding well, for 3-down in the box.

The .375 RUM with its rebated rim was trickier to get feeding right, and did require more extensive tinkering and polishing and a stronger magazine spring. 4-down in the box.

Sabot: Have you had a 375 HH converted to 375 Rum? I have heard from several people including RIP that the feed rail work is a bit tricky. What action did you start with, Mod. 70 or CZ 550?

Sorry, but i have not personally made this conversion. I can only suggest that you listen to those that have done it. I am still left wondering how the conversion to the 378 could be easier than to a 375 RUM, but i am willing to learn!

quote:

Originally posted by Sabot:
Sorry, but i have not personally made this conversion. I can only suggest that you listen to those that have done it. I am still left wondering how the conversion to the 378 could be easier than to a 375 RUM, but i am willing to learn!

The .375 RUM conversion of a .375 H&H CZ 550 Magnum is trickier, more time and labor intensive, because the rebated rim will let the bolt ride right over the top of it. You have to thin out the rear undersurface of the feed rails and put in a stronger spring to push up a little harder on the rear end of the cartridge. Additionally, putting a spacer in the rear of the magazine box to block it down to 3.620" length will also make the 3.600" max COL RUM feed better out of the box, and better have everything polished slick.

For the .378 Weatherby, opening the bolt face is an easy, routine thing for the gunsmith. Then, the bigger back end of the .378 Wby makes it easier to get to feed right.

And don't forget, that the .375 RUM will not quite clean up the .375 H&H shoulder, so you will end up with a partly rounded looking .375 RUM shoulder at the neck-shoulder juncture, as John from Oz got in his M70 conversion. It is not enough to affect headspacing and function, John said, but it is not the perfect chamber we would rather see. So one must whack off the barrel threads and set the barrel back. That really makes the conversion more time and labor intensive with the .375 RUM than with the .378 Wby. Or, you can rebarrel to get the .375 RUM, with extra expense,

The slickest CZ 550 Magnum conversion of all, is from .375 H&H to .375 Wby. Just run the reamer in and you are usually done. If the rifle was good before you started, it will be better after.

I have done this conversion to a Whitworth Mark X, a Winchester M70 Classic Stainless, and a CZ 550 Magnum Safari.

With the CZ 3.8" box, one can load the bullets to 3.75" COL using the extra cannelures on the Barnes TSX, North Fork SP, or GSC FN/HV. Then, the .375 Wby will have an effective case capacity like the .375 RUM and can beat 2800 fps in a 25" CZ barrel, with 300 grain bullets.

The current .375 Wby throat is the one that allows this with good results.

I have done all three conversions.
If you want over 3000 fps with 300 grainers, the .378 Weatherby is the only way to go.

If you want over 2800 fps with 300 grainers, the .375 Weatherby in a CZ 550 Magnum Safari is the smartest way to go.

I got just one more to do before I quit the .375 caliber rifle contracting business: .375/.338 Lapua Magnum, otherwise known as the 9.5x69mm Tornado. Then I might change my handle to Rip375 or Ron375.

Well, Maybe this topic can help me. I have a .338-378 Wby I would like to step up to a .375 or .416. What would be my options without staying with a Wby. case for reduced recoil???

quote:

Originally posted by drdlongshot:
Well, Maybe this topic can help me. I have a .338-378 Wby I would like to step up to a .375 or .416. What would be my options without staying with a Wby. case for reduced recoil???

.416 Rigby: Been there, done that, several times.

.375/.338 Lapua Magnum: In the works for me. The Germans use it and call it the 9.5x69mm Tornado, in their proprietary line of Mauser 98 actioned rifles.

Your .338/.378 Wby bolt face and box will handle any of a number of .416 Rigby based wildcats.

How adventurous are you?

Thanks for the info. Sounds like the Rigby would be the way to go for me.