I have a Mod. 70 in .300 RUM on the way and want to convert it to a .375 H&H. Is the bolt face diameter on a .300 RUM the same as the .375?



In case anyone has done this, did you run into any problems?



Thanks.

I can't address your question directly, but why not have it rebarreled and chambered for .375 RUM? If you're looking to use the same gun to go to a larger caliber, why not use a chambering like the .375 RUM? You don't HAVE to load it to RUM capabilities, but you could if you ever wanted/needed to.

Good luck on whatever you decide.

Take care.

Russ

While there are surely no flies on the .375 H&H, it would be FAR simpler to simply re-barrel to .375 Ultra Mag. This should eliminate any problems with feed rails etc due to the rather major differences between the straight-cased Ultra Mag profile and the tapered H&H profile, as well as the diameter differences along the case lengths.

Making a smaller-diameter case feed correctly from a magazine and receiver contoured for a larger-diameter case could be a very iffy proposition. By changing ONLY the bore dimension and hence the neck diameter of the case, feeding should be largely un-changed from when the rifle was a .300UM. You will also almost certainly save a good deal of money that would otherwise have to be spent in getting the H&H to feed correctly.

Regards from BruceB (aka Bren Mk1)

The RUM is on a 404 parent case and has a .534 head, the 375 H&H has a .532 head, you might get away with it, but I wouldn't want the slop in my rifle I don't think????....but a 375 RUM would be a nice caliber as long as you loaded it down to reasonable velocity...and you would get a lot less pressure, and not have a belt, if that means anything...

Sell the new gun and buy yourself a good Mauser 375 H&H is my suggestion....it will be cheaper or at least a close push.

Will, it's true, the best solution would be to rebarrel for .375 RUM, or else possibly .404 Jeffery.

I would certainly think that the .375 RUM would do a lot of jobs well!

AD

Will,
Ditto all the guys above.
And one more bit of data, the rim on the .404 Jeffery Norma brass is 0.540" and the RUM boltface needs to be opened up a tiny bit for that.

I think the .532" versus .534" rim difference may not be critical, and it may indeed be the same boltface for both factory rifles.

I think about .005" of slop in the boltface over the rim size is the usual smooth feeder.

The catch may be the box and rails, but again, it might work fine. Try it and see ... and let me know if you can beat 6.75# for the completed rifle. If you can't, it Will make my day.

Thanks to all.

It is a toss up between a .375 and a .404. I have another Mod. 70 in .375, so I will see how much different the RUM rails and ramp are to the factory .375 action.

A 6.74# .375 would be handy, though!

I say you got a good start for a 404 jeffery, thats what I'm building mine from.

Will

I think you need a 404 Jeffery Does everything the 375 can and a bit more

http://www.african-hunter.com/reloading_the__404_jeffery.htm

Cheers
/ JOHAN

You're right, but the 404 is still a freak show. High cost dies, brass, bullets, few solid bullets, .....

The case rim diamert for the 300 Ultra is the same size as H&H and smaller than 404, hence the slightly rebated rim.

I would think a 300 Ultra will have problems reliably feeding 375 H&Hs. I know that M70 Push Feeds that were 300 Win and have the 375 magazine box and foller (plus bolt stop shortening and altering the rear of the rails) have problems with 375 H&H.

But it would be easier enough to do 375 H&H and if a problem then rechamber to 375 Ultra.

Mike

Yup, Remington made the 300 RUM with a slightly rebated rim (standard magnum bolt face) so they wouldn't have to modify the M700.