Improving the 375 H&H

IvW

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I own two 375 H&H rifles one is an original ZKK 602 with pop up sight and the other also on a ZKK 602 action has a custom 24 inch barrel.

I am contemplating having the one rechambered to 375 H&H Ackley Improved. (I have a 40 degree die set for the AI)

The reason I want to do this is that here in South Africa we have one of the best bullets available manufactured by Rhino. I love the heavy weights.

I want to use the extra case capacity to shoot these 380 grain Rhinos at about 2350 Fps without excess chamber pressure. I cannot imagine a better combination for all PG through to Buffalo.

The other option is just to rebarrel to 404 Jeff but this is costly and then I need to re licence the firearm.

Thoughts and comments appreciated.
 

Velo Dog

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Here in the States, cutting a rifle chamber out to some "improved" version, generally results in a very sharp drop in resale value of the rifle.
My opinion is, have it rebarreled to .404 Jeffery, even if you have to save up the money over a long time.
If it were my rifle delema, I feel that having an Ackley Improved chamber would always pester me with simmering regret.
Conversely, having a .404 would be worth the wait.
 

sierraone

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Here in the States, cutting a rifle chamber out to some "improved" version, generally results in a very sharp drop in resale value of the rifle.
My opinion is, have it rebarreled to .404 Jeffery, even if you have to save up the money over a long time.
If it were my rifle delema, I feel that having an Ackley Improved chamber would always pester me with simmering regret.
Conversely, having a .404 would be worth the wait.
I thought this was one of those joke threads when I first saw "Improving the .375 H&H!
 

Shootist43

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From everything I've read the AI versions of any caliber are of little to no consequence as far as performance is concerned, from 25 to 50 FPS at best in most cases. If you don't already have a 404 Jeffery rebarreling one of your 375s to that caliber would be my choice. Since you like heavy for caliber bullets anyway they make 450 Gr. bullets for the 404.
 

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You will gain at little more powder capacity and with the heavies that will help some. (I will look up what the difference is when I can get out to my shop for a bit) The reason that I like to improve several different rounds (257 Roberts, 7x57, 30/06 and the 375) is that once you have fireformed the brass to that 40 degree shoulder (I find that I wear the case out before the need to trim the case to proper length happens vs case trimming every two reloads.)
 

JimP

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Also a advantage of the AI in any of the calibers that it is chambered for is that you can shoot the standard round through it if you don't have any of the AI rounds handy.

I also have never seen a decrease in value of a rifle that is rechambered to the improved version. Now perhaps if you had a classic it would go down in value but a rifle that goes out on the hunts with you will only be better.
 

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When H&H set about to improve on the 375 H&H they came up with the 400 H&H. That says something I think.

But, I don't think Rhino makes a .411 diameter bullet. From African Dangerous Game Cartridges by Peter van der Walt:

375 H&H with 380gr Rhino: KE 4,465 ft/lbs
400 H&H with 375gr Claw: KE 5,102 ft/lbs

It will push the same weight faster. Also, a wider surface area to boot.

But, maybe you are back to having to register the gun? Also, more work. Good luck with the decision
 

Shootist43

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IvW, I just looked up some load data for both the 375 H&H and the AI version. The AI version's max load of 88 Gr. of H4350 yields a velocity of 2740 FPS. The max load for the 375 H&H is 81.5 Gr of H4350 for 2645 FPS. In this instance there is a 95 FPS or stated differently a .0359% increase in velocity. Is that really going to make a difference?
 

Ray B

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My friend the late Bill Steigers had two wildcat 375s of which he was very fond, considerably more so than the standard H&H. One was a 404 Jeffery blown out and the shoulder moved forward so that the neck was 3/8" long (one caliber); the other was basically an 8mm Rem Mag necked out to 375, no other changes. I think he liked the 375/404 better but at the time (1980s) 404 brass was scarce so he used the 375/8mmMag more. When I considered getting something in 375 with more umpf than the H&H I went with the 375RUM. Other than Remington pulling the rug out from under it, I have no objection to it.
 

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Hi JimP,

I have no doubt that you have had different experiences with buying, selling and trading rifles with modified chambers than I have had.
That does not mean that either one of us is wrong.
However I guess it does mean that, we shall just have to agree to disagree.

My experiences with such reamed out chamber / modified rifles are as follows:
When I worked in a gun store (Great Northern Guns), here in Anchorage, we periodically received a rifle with a modified chamber, to consign for sale.
My personal experience with those things was that few buyers showed an interest in them at all.
They invariably sold for quite a bit less than they would have been worth, prior to the chamber modification.

Someone once said that "difference of opinion is what makes for good horse races".
So, we have a good horse race here I guess and that is not a bad thing.

Cheers,
Velo Dog.
 
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IvW

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IvW, I just looked up some load data for both the 375 H&H and the AI version. The AI version's max load of 88 Gr. of H4350 yields a velocity of 2740 FPS. The max load for the 375 H&H is 81.5 Gr of H4350 for 2645 FPS. In this instance there is a 95 FPS or stated differently a .0359% increase in velocity. Is that really going to make a difference?

Thanks for that.

I am more concerned about trying to keep the chamber pressures down while at the same time trying to get the 380 grain bullet(great bullet) moving at a respectable velocity. With the powders we have available getting to 2200 fps without undue chamber pressure is proving a challenge. This also affects the practical effective hunting range.

As I understand it the AI version increases case capacity by about 9%(from what I can see on the internet).

I am hoping that this will allow me to get the 380 grain slug to 2300 Fps without excess chamber pressure.

I am not concerned about resale value as this rifle will not be for sale and when my son gets old enough he can rebarrel it to 404 or 500 Jeff, cause he ain't getting my 500 Jeff until I am pushing daisies anyway.
 

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Screw it and DO IT!!! They're your guns so if you want an Improved 375, get the chamber cut to 375 Improved.

Welcome to the world of customizing guns. It's not always about the performance; sometimes it's just having something personalized and unique.

If you're not happy with the Improved version, then you can always rebarrel to another caliber; heck, even if you are satisfied, you may decided to rebarrel something else into something else!

Your $$; your rifle; your fantasy/obsession - Do it.
 

Shootist43

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IvW, before you start cutting metal have you tried Quick Load or some other ballistic software to see what possible variances there might be? If you ask him nicely Alchemist (who lives in Pretoria) has that software and is very adept at using it. He has helped other AH members with reloading issues in the past.

P.S. in my previous post I forgot to mention that the powder charges and respective velocities were for 300 Gr. bullets.
 
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IvW, JMO, but I’d like to see it done just to know if it will work and accomplish your goal.
I do like Shootist43’s idea of using QuickLoads to get an idea of the potential results before metal is cut.
I have read articles by Mike Scoby (Peterson’s Hunting magazine writer) that the 375 AI is what he uses.
Best of luck in your decision!
 

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I have a quick load program, if it has rhino bullets listed I will run some #'s and see what it will do. What powders do you have access to so I can run them?
 

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Improving the 375 H&H?????????

I believe Ruger did that already...........:)
Gasoline, damn it, where's the gasoline.
Oh right, there it is, next to the 375...

Always stoking the fire. Cheers
 

IvW

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I have a quick load program, if it has rhino bullets listed I will run some #'s and see what it will do. What powders do you have access to so I can run them?

Hi that might be interesting, kind offer.

We have Somchem, S335, S355 and S365.

May also be able to get hold of Vihtavuori powder.

Thank you
 

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IvW, I just looked up some load data for both the 375 H&H and the AI version. The AI version's max load of 88 Gr. of H4350 yields a velocity of 2740 FPS. The max load for the 375 H&H is 81.5 Gr of H4350 for 2645 FPS. In this instance there is a 95 FPS or stated differently a .0359% increase in velocity. Is that really going to make a difference?

I may be missing something but I think a 95 fps increase over 2645 is a 3.59% increase?

Regardless, I have a 338 Fed Encore barrel and a Sako 85 Hunter in 338 Fed. No need for both. Started looking at 338-06 and then 338-06 AI since the standard 338-06 wouldn't "clean" the chamber for the 338 Fed. After loads of time and effort to research I just decided to rechamber for the 338 WM. I can always load that one down, the brass is inexpensive and readily available, and it's a SAAMI standard cartridge. There are at least two sets of 338-06 AI specs out there, and the reamer for my barrel manufacturer didn't match the dies available from Redding (or RCBS as I recall). Add to it the need to fireform or hydroform brass, the time, effort, and cleaning required to do so just wasn't worth it *to me*. And I really like the idea of having a unique chambering along with the whole premise behind the Ackley Improved idea, so tried hard to talk myself into the AI.

That's a long winded way of saying that I don't think the 375 H&H AI has standard specs and therefore the reamer and the available dies may or may not match. They certainly didn't for the 338-06 AI. Guess I'd vote for the 404J.
 

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Here in the States, cutting a rifle chamber out to some "improved" version, generally results in a very sharp drop in resale value of the rifle.
My opinion is, have it rebarreled to .404 Jeffery, even if you have to save up the money over a long time.
If it were my rifle delema, I feel that having an Ackley Improved chamber would always pester me with simmering regret.
Conversely, having a .404 would be worth the wait.
I have to agree with Velo here but..... If your going to keep the rifle for ever and ever I get the idea. I know when I buy a rifle I stay away from any or the AI's even though I a reloader. I don't want to get in a situation where I'm hunting somewhere and my ammo got lost, damaged, stolen, forgotten, etc and cant go to the store and by more in a pinch.
 

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