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Anonymous
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375H&H Magnum to the new 400H&H
#84983 - 31/08/07 06:32 AM

Question:

Can one rebore a 375H&H Magnum (Belted) DR to the new 400H&H? I was told the cases are identical so it should just be a matter of recutting the bore to .411?

Any help would be appreciated.

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bonanza
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Re: 375H&H Magnum to the new 400H&H [Re: ]
#84991 - 31/08/07 11:30 AM

No. You need to bore out at least 55 thousands otherwise you will get "reverse rifling". The drill will chatter on the existing rifling and produce ghost riling in reverse.

How do I know, I asked the man who re-bored my .303 to .358. Also you will have to get it re-regulated.

I know you question is hypothetical, but I also have a .375 H&H belted DR and love it the way it is. In fact, instead of of amping it up, I back it off to flanged velocities to save the action.

Which is a great seqway(sp) for belted DR's and modern bullets. The predominate issue with belted DRs is the high pressure stretching that action loose. However with modern bonded and mono bullets, one can reduce velocity and still retain good penetration. A slight(~300-400 fps) reduction in velocity yields a large reduction in pressure(~3-4 tons).

This makes belted DR practical. So a new DR in 400 H&H would be super cool, as long as you back off the charge just a wee bit.

B.

--------------------

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400NitroExpress
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Re: 375H&H Magnum to the new 400H&H [Re: ]
#84994 - 31/08/07 12:54 PM

Sure. Paul Roberts has sold more rebored doubles than anybody I know of. He rebored, rechambered and reproved many .400/.350 and .350 No. 2 rifles to 9.3X74R. Another common rebore is .318 Westley Richards to 9.3X62 rimless, an increase of .037". The .450 NE to .470 NE is also common, an increase of .025". Going up .036" to .411" shouldn't be a problem. Most, if not all of Paul Roberts' (J. Rigby; J. Roberts & Son) rebores were done in the US by Cliff Labounty. The special machinery he made for reboring doubles went to Jim Dubell, who is the only one in the US I know of who can do it.

The issue is remaining wall thickness, and you need to make sure you have enough. In any event, it would really need to go back to England or Europe for re-proof. I know where there's a .475 rebored from .450 that blew up recently with normal loads. It had not been re-proved. Use of monos in a rebored double would be a really bad idea.

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"Serious rifles have two barrels, everything else just burns gunpowder."

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bonanza
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Re: 375H&H Magnum to the new 400H&H [Re: 400NitroExpress]
#85009 - 01/09/07 12:49 AM

I spoke directly to Jim Dubell and he said he won't do a double for the reason I mentioned above.

I agree that using monos in a re-bore is a bad idea, but are perfectly fine in a new rifle.

--------------------

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400NitroExpress
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Re: 375H&H Magnum to the new 400H&H [Re: bonanza]
#85011 - 01/09/07 02:01 AM

Quote:

I spoke directly to Jim Dubell and he said he won't do a double for the reason I mentioned above.

Like I said, Jim got that rig from Cliff Labounty, and Cliff rebored many, many DRs with it for Paul Roberts. I've handled a bunch of them and can tell you that everything from .010" to .047" increases were common, and .055" certainly was not. Aside from a few .303s rebored to 9.3X74R, I've never seen another taken up as much as .055". A minimum of .055" would essentially mean that doubles can't be rebored as almost none would have enough remaining wall thickness to survive proof and, thus, be safe.

For example. Aside from the clunks, most decent quality doubles rifles have a min wall thickness at the muzzle of under .100", some considerably less. A .303 built with .100" min wall thickness would thus have a muzzle diameter of .511". Taking it up .055" to .366" for a 9.3 would result in a min wall of .0725". As a friend of mine expresses it - "Cat shit a monkey!". Even if it passed proof, that's razor thin. No thanks. Keep in mind that most doubles don't quite have .100" min wall to begin with.

You either didn't understand what Jim said, or he's having problems that Cliff certainly did not. Think about it. Your .303 rebored to .358 is an increase of .047", not .055". I personally know of another, probably one of the last that Cliff did, that was a .470 to .500, an increase of .036". If Jim really is having such problems, I guess DR rebores will have to go to Europe.

Quote:

I agree that using monos in a re-bore is a bad idea, but are perfectly fine in a new rifle.

Sorry but, you're dreaming there. Monos aren't safe in any double.

--------------------
"Serious rifles have two barrels, everything else just burns gunpowder."

Edited by 400NitroExpress (01/09/07 02:23 AM)

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bonanza
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Re: 375H&H Magnum to the new 400H&H [Re: 400NitroExpress]
#85017 - 01/09/07 02:59 AM

Jim's specific concern was the "squeeze" causing an off center bore. I'm not going to argue with the guy, but he seems uninterested in doing doubles.

I thought a 303 was .303", it's .312" my mistake.

We'll have to agree to disagree regarding the monos. I shoot monos exclusively in my Merkel, but would not dare in my Vintage rifles.

In fact, I don't like shooting Woodleigh solids either. I will only shoot them enough times to find a regulation load. After that it's Hornady softs.

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400NitroExpress
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Re: 375H&H Magnum to the new 400H&H [Re: bonanza]
#85018 - 01/09/07 03:18 AM

Quote:

We'll have to agree to disagree regarding the monos. I shoot monos exclusively in my Merkel, but would not dare in my Vintage rifles.

In fact, I don't like shooting Woodleigh solids either. I will only shoot them enough times to find a regulation load. After that it's Hornady softs.

I've personally seen new rifles damaged with monos, and vintage rifles used with monos that weren't - yet. Holland & Holland has had NEW (brand new, with barrels of top quality modern steel) double rifles ruined before they were even finished (being regulated in the white) with monos. The "new vs old" argument regarding monos in double rifles is pure myth. It's a matter of wall thickness and nothing else. A clunk with .125" min wall will probably handle quite a few before damage occurs, but it will eventually.

The most insidious part of the problem is that so few even know what it looks like. I know a guy, a VERY sharp and experienced double rifle guy, who bought a very expensive best DR that had serious rifling imprint on the outside of the barrels. He didn't have clue until his gunmaker saw it.

--------------------
"Serious rifles have two barrels, everything else just burns gunpowder."

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Anonymous
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Re: 375H&H Magnum to the new 400H&H [Re: bonanza]
#85020 - 01/09/07 05:29 AM

Interesting views. I was examining some recent books that show the case shoulder has been pushed back on the new 400 Holland, along with very slight differences here and there on the rim. I'm not to certain it will convert due to the chamber charactistics.

Hell, maybe I should just rebore the sucker to 450/400 3" if wall thickness is nominal..

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400NitroExpress
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Re: 375H&H Magnum to the new 400H&H [Re: ]
#85021 - 01/09/07 05:42 AM

Quote:

Hell, maybe I should just rebore the sucker to 450/400 3" if wall thickness is nominal..

I had the same thought and briefly looked at the .375 and .450/.400 drawings. The .400 is only 2.1" to the shoulder, with a .440" neck. The .375 is 2.4" to a .450" shoulder, so I'm not sure that the .450/.400 3" reamer would entirely clean up the .375 chamber. I haven't looked at it very hard though.

Maybe .500/.416?

Are the .375 bores shot out?

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Anonymous
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Re: 375H&H Magnum to the new 400H&H [Re: 400NitroExpress]
#85027 - 02/09/07 01:35 AM

.500/.416 is an interesting load. Bores are in fine shape, was just a curious option I was brewing about...

I do really like the 375H&H magnum round, and have never had any "real" issues in my DR's chamered in it. Perhaps best is left alone.

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4seventy
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Re: 375H&H Magnum to the new 400H&H [Re: 400NitroExpress]
#85038 - 02/09/07 06:57 PM

Quote:

Holland & Holland has had NEW (brand new, with barrels of top quality modern steel) double rifles ruined before they were even finished (being regulated in the white) with monos.

400,
Any record of how many rounds were fired in this particular incident?
Also, what was the actual damage to these barrels, as the "ruined" description could mean any number of types of damage?
There was mention a while back of an article about this gun being written up in DGJ. Does anyone know which issue that was?

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500Nitro
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Re: 375H&H Magnum to the new 400H&H [Re: 4seventy]
#85040 - 02/09/07 07:05 PM

Guns will still shoot even if the rifling marks
are on the outside of the barrel.

It does not mean they are ruined.

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Bramble
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Re: 375H&H Magnum to the new 400H&H [Re: 500Nitro]
#85047 - 03/09/07 12:21 AM

Yes please.
I would love to see some pictures of a rifle in this condition. I have heard it mentioned so often and I still cannot conceve of how it can happen without something else letting go at the breech first so huge are the forces required.
I am not questioning anybodys word, I just want to see for myself.
I cant imagine in this litigation plagued society that H+H would build a vastly expensive rifle that would not digest whatever the client might throw at it given that mono's are a commercial load.

Regards

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BigFiveJack
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Re: 375H&H Magnum to the new 400H&H [Re: Bramble]
#85104 - 04/09/07 10:40 AM

Could a rechambering to .369 Purdey work? This way no

reboring is called for and one gets the benefit of a

reduced pressure, rimmed cartridge.

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Jack

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bonanza
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Re: 375H&H Magnum to the new 400H&H [Re: BigFiveJack]
#85107 - 04/09/07 01:07 PM

I doubt you would ever see rifling impressions on a new rifle as the boring is done more precisely and the mono bullet is not obtured(sp)in the bore. I have spoken to gun makers, Barnes directly and gunsmiths to come to my conclusion. However, I have seen these impressions on a vintage DR on a visit I made to Champlins. When held up to the light you can see a ghostly image on the barrels in the pattern of the rifling.

--------------------

"Speak Precisely" G. Gordon Liddy.

"Life is absurd, chaotic and we must define its purpose with our actions" Abert Camus

"I''m the dude playing a dude disguised as another dude."

"Yo! Mr. White"

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400NitroExpress
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Re: 375H&H Magnum to the new 400H&H [Re: 4seventy]
#85136 - 05/09/07 01:09 AM

Quote:

Quote:

Holland & Holland has had NEW (brand new, with barrels of top quality modern steel) double rifles ruined before they were even finished (being regulated in the white) with monos.

400,
Any record of how many rounds were fired in this particular incident?

The damage was done while the rifle was being regulated. As I recall, they said less than 60 rounds.

Quote:

Also, what was the actual damage to these barrels, as the "ruined" description could mean any number of types of damage?
There was mention a while back of an article about this gun being written up in DGJ. Does anyone know which issue that was?

The damage was rifling pressed through to the outside of the barrels. I heard the story in their shop. Ross Seyfried mentioned it in an article in DGJ, IIRC, in 1994 or so.

--------------------
"Serious rifles have two barrels, everything else just burns gunpowder."

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400NitroExpress
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Re: 375H&H Magnum to the new 400H&H [Re: 500Nitro]
#85137 - 05/09/07 01:14 AM

Quote:

It does not mean they are ruined.

Actually, in this particular instance, it does. With the barrels damaged like that, the gun is out of proof and can't be legally sold. While you could strike off the barrels to get rid of the rifling imprint and reblack, Holland apparently had a problem with that idea, and the barrels were replaced.

--------------------
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400NitroExpress
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Re: 375H&H Magnum to the new 400H&H [Re: Bramble]
#85138 - 05/09/07 01:35 AM

Quote:

Yes please.
I would love to see some pictures of a rifle in this condition. I have heard it mentioned so often and I still cannot conceve of how it can happen without something else letting go at the breech first so huge are the forces required.

Yes, that's a common misconception. It has nothing to do with pressure.

Quote:

I am not questioning anybodys word, I just want to see for myself.

I have several good friends that I help to locate double rifles for. When a nice candidate is located, an offer is made contingent on evaluation by a gunmaker. Of the last five that have gone to the gunmaker (in this internet world, I usually don't see them until they get there), two turned out to have rifling imprint on the outside of the barrels (overstressed rifling). I've seen dozens of them, and have personal experience with it. A hunting partner insisted on shooting Barnes X in his 9.3 double despite warnings. Roughly 40 rounds of Barnes X left the barrels with severe overstressed rifling.

Quote:

I cant imagine in this litigation plagued society that H+H would build a vastly expensive rifle that would not digest whatever the client might throw at it

Holland doesn't warrant their DR barrels with monos, at least they didn't the last time I asked about it, and they're far from the only ones that don't.

Quote:

given that mono's are a commercial load.

Not for double rifle cartridges they're not.

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400NitroExpress
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Re: 375H&H Magnum to the new 400H&H [Re: bonanza]
#85139 - 05/09/07 01:42 AM

Quote:

I doubt you would ever see rifling impressions on a new rifle as the boring is done more precisely and THE MONO BULLET IS NOT OBTURED IN THE BORE.

Correct, they don't obturate because they can't, and that's what does the damage.

Quote:

I have spoken to gun makers, Barnes directly and gunsmiths to come to my conclusion.

So have I, and I can tell you that Barnes has not done any testing with monos specific to double rifles. Moreover, they were consulted beforehand about shooting the X bullets in the rifle referred to above - and they were wrong.

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