Some of my favorite hunting rounds have been the .300 Weatherby and .340 Weatherby.
Thinking the .375 Weatherby would be a good all around rifle for a one gun Safari.
I have two donor Pre 64 Mod 70 actions. One from a .300 H&H and the other from a .375 H&H.
I have read about everything I could on several forums regarding this conversion. Curious who else has done one of these conversions on a pre 64 Mod 70 original magnum length action? Trying to gather some initial information prior to talking to a rifle builder. Getting mixed information on what is entailed. Some are saying the existing magazine box will work, the factory follower will work. Some are saying the feed rails do not need to be modified. Who has experience with this conversion? Would the .375 H&H action work better as the donor action or would the .300 H&H be best? If a new magazine box is needed , who can supply one? Going to be starting with a new barrel and bottom metal.

First, I have a 375 Weatherby reamer for sale.
As everyone knows, all pre 64 Model 70s are made for the 30-06 and were hogged out for the H&H length cartridges. Lest anyone think they are different actions. In 64, the action was lengthened to the H&H length for everything from 308 to H&H. I've done plenty of those.
Anyway, if you have an action originally for the 375 or 300 H&H, the Wby should fit as is. The OAL is the same; just the shoulder is bigger; the 375 Wby is just a H&H with a less tapered case.
I have not done it on the actions you have, but I can envision it. Not a big deal.

It has been suggested many times to make four 375 Wtby dummy rounds with whatever bullet you plan to use and run those through both actions

This act alone will tell you an awful lot

Not on Pre 64 but have on post 64 (CRF).
Love the gun and caliber!
If you handload H4350 is the powder for the 375 Wea.
Good luck on your project.

EZ

I have an FN sako that was 375 H&H blown out to 375 Weatherby. Does not feed 100%. I forget which side.

Looks like the feeding will not be a major issue. Have a very experienced builder who can handle about anything. He is saying some rail work. D’Arcy , as always great advice. Wish you had a extra one of your new LX-1 actions available at this time.
Curious to those who have~favorite .375’s , what are your rifles weights , scoped and ready to go? I am wanting to go with a S&B 1.5-6X42 and having a hard time getting much below 10lbs with a wood stock and 25” barrel.

I shot a 300 H&H using a 30-06 length action modified for years..DEnnis Olson did the metal..

What you suggest has been done many many times..

4WD, my Ruger RSM is 11.25 lbs scoped with a Leupold 1.5-5x20. I am sure that this is considered heavy for a 375 but it is a pleasure to shoot as the recoil is so mild. I have several friends that also have the same rifle and feel the same way. I never had a problem carrying it but then I wasn't climbing mountains with it either.

Just a thought. Have you considered .375 AI.
A standard 375 H&H head stamp will get you
across the pond to Africa. Otherwise you need
to find 375 WBY brass or shoot factory.
Good Hunting,

Tetonka
DRSS & Big Bore Nut (Left hand thread of course)

got a 340 wthby on a 338 win mag chambered m70 push feed... no issues

I have done one custom build from a pre 64 md 70- well my Rifle builder did. When I acquired the rifle it was a very well professionally done 7mm-300 wby. The action was a Magnum H&H pre 64 Md 70, High end Brown Precision stock , Canjar trigger, and a Custom Stainless fluted barrel. The Cartridge I wanted to go with originally my Builder told me I would be better off with a post 64 CRF Model 70-said it was a tadd longer than the pre 64. I have not verified this. I settled on a 338 rum with a bartlein fluted 5r barrel 9.3" twist. I have attached two links that helped me have some understanding of Pre 64 Md 70 actions.
https://pre64win.com/products/complete-pre-64-action
https://pre64win.com/blogs/wel...112881286-first-post

I will verify your findings; all pre 64 Model 70s receivers are 30-06 length. When they put the H&H length cartridges on them, they opened them up top, bottom, and side, to do so.
The first design change in 1964 was to lengthen the receiver to accommodate the H&H lengths, without alteration, and blocking the mag box off for everything else. So yes, the post 64 action is far superior to the pre, for the H&H length cartridge. I posted a picture of the pre 64 mods, in another thread here.
Also the post 64 model was the first one to be made from a forging; contrary to popular belief. Pre 64s were not made from forgings.
As for the claw extractor/CRF feature; remember why it was developed in the first place; under the Turkish contract; to prevent low trained troops from double feeding. Germany did not adopt it for ten more years; push feed was good enough IF you are trained on your equipment. I prefer the smoother feed Model 70s, and have never had a problem with one, since literally, 1968. Had at least 25 of them.
I know guys on AR are enamored with the CRF; and I also find that Americans will not train with their rifles. Off topic here.

dpcd "Off Topic Here". But you have been there. And I just learned the History of the origin of the CRF in this action today.
Thank You

If I had a pre-64 Model 70 that was originally in 375 H&H I would not convert it to 375 Weatherby. It's too classic of a gun to change. That being said I have a Rem XCR II in 375 Weatherby that weighs 7 1/2 lbs with scope unloaded. It's awesome. 300g A-Frames at 2800 fps or 350g Woodleighs at 2550 fps. It's accurate, light and powerful.

4WD,

One thing to consider with the 375 WBY is if you use the 300 gr TSX or ACB the magazine on the Pre 64 will only allow you to load the round to about 3.58 inches for dependable feeding. What this means is that you'll run out of powder space before you reach max load. Yes! I used a drop tube and all the tricks. If I built another one I'd probably use a CZ and get one more down. Having said that the 375 WBY is a great all arounder. Mine has accounted for red duiker to buffalo and brown bear. Great round.

Mark

I prefer the 375 H&H for buffalo, as its kinder to bullets, and you get better results..according to several PHs who are gun buffs and Doctari suggested this to me at SCI some many years ago..I tried it and Im convienced they are correct on Buffalo, Hippo, elephant, On plainsgame it makes no difference to me, like both calibers but the H&H recoils less and I appreciate that..

Thats the rest of the story take it or leave it, remember its your safari and the choice is yours, wouldn't have it any other way..

DPCD and Ray are correct.

I currently own an original pre-64 M70 in 375; and have owned an Al Biesen pre-64 M-70 375 re-chambered to 375 WBY. The WBY rifle was built for Alaskan hunting. It was an excellent rifle with a
reinforced/glassed original stock. (Always a good idea.)

I prefer the 375 WBY over the Ackley version
though they are identical ballistically.
The WBY is good for top loads or bullets heavier than 300 gr. Mine had G&H mount with Leupold 4X Alaskan scope.
One gets a bit more velocity with the WBY but most
African or Alaskan game would not know the difference.

quote:

Originally posted by MARK H. YOUNG:
4WD,

One thing to consider with the 375 WBY is if you use the 300 gr TSX or ACB the magazine on the Pre 64 will only allow you to load the round to about 3.58 inches for dependable feeding. What this means is that you'll run out of powder space before you reach max load. Yes! I used a drop tube and all the tricks. If I built another one I'd probably use a CZ and get one more down. Having said that the 375 WBY is a great all arounder. Mine has accounted for red duiker to buffalo and brown bear. Great round.

Mark

Hey Mark ,
Sounds like you enjoy and hunt with your .375 Wearherby.

Did your friend Lon Paul build it for you? Ideally what would your overall cartridge length be with the Barnes TTSX 300 grain be? What would your magazine box length be?

Not sure about opening up a Pre64 Win to accommodate a 3.8” long magazine box. Maybe our friend D’Arcy will chime in. He has so much experience on these builds.

4WD,

Lon Paul did build the rifle and it is a no nonsense working rifle beauty.

I've not tried the 300 GR TTSX as the TSX was really too long itself. I ran out of powder capacity before reaching max pressure. Although I did get 2725 FPS. I switched to the Northfork 300 which was shorter and got 2765 FPS. I've finally settled on the 270 TSX that I can drive at 2900 FPS for everything.

Regardless of the bullet you choose you can only load the cartridges to max 3.58 for them to function in the Pre 64. I may be wrong but I think the Dakota 375 mag box might be a little longer and there is the CZ. Of course if you use a Nosler partition that has been loaded in the 375 WBY factory stuff for years you'll have plenty of room.

The 375 WBY can benefit from a longer barrel and I wish I had specified 26" on mine.

Mark

Get a Model 70 classic rifle in 300 Rum and rebarrel it to 375 Weatherby.
Do a Wyatt Outdoors magazine box conversion on it pick up a little more length in case you decide to seat it out a bit.
Might as well Blueprint it while you're at it, the Factory threads and faces on those are pretty pathetic, but do clean up nicely without a fuss.

In the case of a Pre-64 don't fool with it.
The classic 70 will do it better and cheaper.