I've been reading a lot of good stuff here regarding the 375 Weatherby and the new freebore specs. I have been giving some serious consideration to having my 375 H&H opened up to the 375 Weatherby too.

However, what if you just used the Weatherby throating reamer on a 375 H&H? With judicious reloading and using powders like H4895, I don't see why a person couldn't increase the muzzle velocity of a 270 gr. bullet by maybe 75-100 fps. This was the original intent of the freebore, increase velocity using the standard case by using relatively quick burning powders. It's nothing new, the Germans experimented with it before WWII.

True the 375 Weatherby fire forms easily from H&H brass, but if you are satisfied with a modest velocity increase, it would be simple and factory ammo should perform well.

Has anyone tried this approach?

Grove,

You could do that and as you increased the freebore you would make the powders such as 4064, 4895 etc burn rates more suitable for the 375 H&H.

But you would probably need to freebore to a quite a large degree. For example, the 378 and 460 Wby are .75" from case neck to rifling and a 416 Wby is basically a conventional chamber. Based on my calculations the 378 for example can use about 6 to 7 grains more powder than loads from the 416 Wby would indicate to be the case. On the much smaller H&H powder charges that would translate back to perhaps 4 grains.

But that would not be enough to get the full potential from the 375 H&H case capacity and powders in the 4350 burn rate would give very poor velocity.

But if you were to throat a 375 H&H to current 375 Wby freebore you would not have much more freebore than a standard 375 H&H already has. Load a bullet backwards in your 375 cases and you will see you can have them sticking out a fair way.

Mike

Mike375,

I keep reading your posts where you say that the 4350 series powders "...give poor velocity.". I'm just curious to hear why you think that. My standard .375 H&H load is 80 gr. of H-4350 behind a 300 gr. Hornady. Granted, I don't know if I could load a 300 gr. Barnes X in front of that much powder. But with the Hornady, I get 2550-- I got 2640 with 81.5 gr, which was max. I backed off to factory, just to be safe.

That's with a 24" barrel, and current-production Hodgdon 4350.

Anyway, that doesn't seem like "...poor velocity..." to me. Not trying to pick a fight or anything, I'm just curious. I learn an awful lot reading these forums.

Pertinax

Pertinax

Is that with 300 Hornady round nose.

You will get more of the H4350 into the case, which is the Australian powder, and from I have been told the H4350 you have is at about IMR 4350 burn rate. Our current batchs are like IMR 4831. Funny eh...made in Australia but Americans get the latest stuff before we do.

In a Model 70 and 82 grains of IMR 4350 I have been over 2600 with 300 grain Hornady round nose but very compressed.

Try the 270 Hornady Spire point.

Are you neck sizing or full sizing. Just asking because there is usually a couple of grains difference in powder capacity.

Mike

Ditto Mike375, if he is stuck with the old H4350 and does not have access to the new H4350 Extreme.

The standard .375 H&H has throat consisting of 0.1750" freebore plus 2 degree leade.

The new .375 Wby has 0.3700" freebore plus 1 degree 2 minute leade, so they say.

The .375 Weatherby has a 12 percent increase in case capacity over the .375 H&H, and combined with the Wby throat, it gives meaningful gains over the .375 H&H in velocity/pressure, take your pick.

I kind of like 300 grainers at 2740 fps for an even 5000 ft.lbs. at pressures below .375 H&H max loads. It is a breeze.

And the slow bullet crowd can get 2400 fps 300 grainers simply by firing the standard .375 H&H factory loads in the .375 Wby chamber. They will flinch less too, because the recoil is then less than from a .375 H&H firing the same ammo. This makes the .375 Wby the ultimate DGR in any hands.

Old pros can use full power loads with tough bullets in the .375 Wby.

Greenhorns can fire factory .375 H&H ammo in their .375 Wby's and improve their marksmanship and lethality, until they learn to handle the full power stuff.

Mike375:

It is the "extreme" version-- I've not seen any other kind in the couple of years I've been reloading for .375; didn't realize that there would be that much difference year to year (and continent to continent!).

I'm full length sizing, but trying to do the minimal resizing to make the cases fit. 80 gr. is a compressed load-- there's a nice crunching sound as the bullet is seated (RN Hornady). I have not had any of the cases swell though.

I'm thinking about the Weatherby conversion, but dies are expensive, brass is expensive, and hard to get. Probably just leave well enough alone for now.

But I like the idea.

Pertinax

Pertinax,

The 300 Hornady round nose is a very short bullets compare to the pointed bullets and especially when compared to the 300 grain Barnes X. If were to use the 270 Hornady Spire point you dind that load you are using would be really compressed and velocity would not be much greater than you get with the 300 grainers.

The "extreme" powders are all made in Australia but new batches and new powders such as Retumbo seem to get released to Hodgdon before they are in Australia.

Mike

RIP,

How is it there would be less felt recoil shooting a 375 H&H cartridge in a 375 Weatherby than in the H&H caliber rifle? (I am assumming the rifles are the same weight). May be a stupid question but I am not a ballistics or reloading expert. Thanks.

Bwanahile

When the 375 H&H is fired in the 375 Wby chamber the larger chamber of the 375 Wby results in lower pressure and hence a drop in velocity.

Thus if you had a load, factory or reload, in the 375 H&H that did 2550 f/s in your standard 375 H&H and then rechambered your 375 H&H to 375 Wby then the same ammunition would drop in velocity to perhaps 2450 or so, hence there will be a reduction in recoil.

Mike

Mike375 is correct. It is so. I think 100 fps to 150 fps is the amount most .375 Wby rifles will slow down a .375 H&H factory load, assuming the 0.3700" freebore version, not 300 fps as Boddington said. Craig is not perfect, just prolific.

Craig must have been remembering back to the old sloppy throated 3/4" freebore of yore. This .375 Weatherby yore is no more. Remember, .3700" freebore is what you want, and a 1 degree 2 minute leade.

RIP:
Please explain to me what 1 degree 2 minute leade means. A picture would be helpful.

Thank You
Paul K

Who sells the 375 Wby reamer with 0.37" freebore and 1 degree 2 minute leade? Or who has one and will do the job on a Whitworth? Thanks.

Thanks for the explanation guys.

Paul K,

Here is the link to the Clymer data base of reamers

http://www.clymertool.com/cgi-bin/reamer.cgi?

You will see you select from rimmed, rimless, belted and Weatherby. That will bring up a drop down list and when you select the cartridge you will see what leade angle is.

Fla3006

Those reamers will be Wby specifications so a Clymer, JGS, Manson etc reamer will be the same unless you specify different. Of course quality of reamer will vary and JGS and Manson would be two the ones seen at the top of the heap.

Where Wby reamers are different is the freebore diameter is smaller and ideally should be very close to bullet diameter and in fact the specifications call for that.

However, the 378 and 460 are the only two Wbys with the very long freebore. All the others with the exception of the 240 and 416 are at 3/8" freebore. That does not necessarily mean the bullet will be 3/8" from the rifling but the case mouth will be 3/8" from the leade into the rifling.

Mike

Mike375:
Thank You.

Paul K

quote:

Originally posted by Paul K:
Mike375:
Thank You.

Paul K

Ditto.

The leade is the funnel shaped portion of the throat beyond the parallel sided freebore section of the throat.

Leade angle is the semi-angle ("per-side" angle) of the leade that tapers down and merges into the rifling lands.

It's a gentle bullet funnel.

Throat = freebore plus leade.

Check out the pictures on the Clymer site.