how many PSI is a ton of English proof I have tried to find the answer for a double rifle I have the listed proof is 18 ton per square inch

The person you need to talk to is 400 Nitro Express who posts here. However I can tell you that the tons used in British proofing are not dirrectly convertable to PSI. They are measured in two intirely different ways. The Brittish only measures reverse thrust,by curshing a copper disk behind the proofing load, while PSI is chamber pressure in pounds per square inch, which measures the pressure against the chamber walls. Mark can get into the science of this better than anyone I know.

CAUTION DO NOT attempt to convert strait accross from Britt tons to PSI!

More info please. Make and caliber for a start. There is a big difference between the load it was regulated with and “PROOF LOAD”
Why do you need to know the proof presher? I don’t think there is any direct correlation as the systems were very diferant.You should never come close shooting the load it was regulated with. 18 ton per square inch is a lot of pressure. That is about the pressure level of the 375 H&H flanged or about 2tpsi below the rimless version 375 original loadings.
Most of the “Double” calibers were loaded too much lower pressure. 470-14 tpsi, 500 3in-16 tpsi and so on.
Bill

the gun in question is a 375 H&H rimless. build in the early 1960

OK, help me out here. This is a Heym from the early 60s, right? Where are you getting the "18 tons" from? Unless this rifle was re-proved in England, it shouldn't say anything in "tons". Proof marks should be in BAR. What exactly do the proof marks say?

Original British proof standards were measurements of bolt thrust in copper units of pressure, not PSI. The simple answer to your question would be utterly useless to you. What we need to know is what this rifle is proved for.
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"Serious rifles have two barrels, everything else just burns gunpowder."

this is a gun listed on guns america and I wanted to know how the tons shown on the barrel flats related to psi that I know, Sorry for the confusion, I just wanted to know how tons related to psi. RNB

quote:

Originally posted by rnb:
this is a gun listed on guns america and I wanted to know how the tons shown on the barrel flats related to psi that I know, Sorry for the confusion, I just wanted to know how tons related to psi. RNB

I understand what you're trying to do and it doesn't work. It doesn't convert to PSI. It's more complex than that. "18 tons" and "PSI" are measurements of clean different things using entirely different measurement methods.

"18 tons" is the operating "pressure" that a British rifle was proved for between 1955 and 1989. This is an expression of bolt thrust in long tons measured by copper crusher (the amount of pressure exerted by the case head on the breech face measured by the "crush" of a copper pellet). This is bolt thrust, NOT CHAMBER PRESSURE, NOT PSI. The British were unique in that they alone never used chamber pressure. The simple answer to your question is 18 tons X 2240 = 40,320 BaseCUP. It's axial Copper Units of Pressure, not CUP, and not PSI (which are both radial pressure measurements). As it is not convertible to chamber pressure (CUP or PSI), it's of no value to you.

After the UK joined CIP, the original bolt thrust "pressure" standards of the British cartridges had to be converted to chamber pressure via testing, as the two are not convertible. Chamber pressure is measured radially (on the chamber sidewall, not the breech-face). Using .375 Flanged Magnum as an example, as it is an 18 ton cartridge:

Original British bolt thrust standards: 18 long tons BaseCUP

Current CIP chamber pressure standards: 3250 BAR/47,137 PSI

The two above standards are the same, but again, represent measurements of different things by entirely different methods. Other "18 ton" cartridges can have entirely different chamber pressures from that of the .375, for the same reason.
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"Serious rifles have two barrels, everything else just burns gunpowder."

Is there a good book that has this kind of info? What is a good book about double rifles.

Originally posted by rnb

quote:

I just wanted to know how tons related to psi. RNB

For all practicle purposes you should not even try to compare the British proof system to PSI. They are two differant measurments of two differant forces.

The British understood how "bolt thrust" effected wear on the the hinge pin of a double rifle. It works like this, as the bullet travels down the barrel and there is pressure in the barrel it pushes the case back onto the reciver. In turn that force pushes the barrels away from the reciver causing stress on the hinge pin.

The British proof system measured the amount of Bolt thrust of the case by the use of some kind of copper disk method that I really don't know much about, but others here especially the previous poster can explain.

It would seem apparent that the higher the pressure the higher the bolt thrust but that isn't neccisarally the case when comparing differant cartridges. For example a .222 with a 55 gr. bullet will produce high pressure but the bolt thrust created won't work as hard against the reciver of the rifle as it will if you have a 500 gr bullet with equal pressure.

There are other factors that fit into the equation such as case design that effect the amount of bolt thrust further confussing the matter and it makes perfect since that the British would have just side stepped all this by going to the hart of the matter and comeing up with a system that measured bolt thrust instead of chamber pressure.

I'm pritty sure that proof houses oil the cases of proof loads in order to artifically increase the bolt thrust. I went once with a gunmaker friend of mine to the proof house in Munich when he had a couple of his rifles proofed. I just don' remember if they did oil the cases then or not. Anyway what they do in Munich dos'nt mean they do the same in the Brit proof houses.

Seems to me to be some confusion here with everyone talking about 3 or 4 different things. rnb, the direct conversion from the 'Long' ton as a weight is 2240 pounds therefore if a weight of 1 ton is sitting on 1 square inch there are in fact 2240lbs sitting on that square inch. Quite straight forward really and pressure can be expressed in tons per square inch or pounds per square inch (psi) using the factor of 2240.

Now though, as is being pointed out on this post, the tricky part is just where the pressure measurement is being taken, and whether the measure is expressed as direct pressure or copper crushing units. As far as expressing this measurement where ever or how ever it is made, you still come back to the conversion as I have set out above.
If it is bolt thrust or chamber pressure, measured in copper units and 'converted' to tons per square inch by the person doing the pressure testing, then that can be expressed as psi.

rnb asks for conversion from tons per square inch to psi and that is simply 40,320 psi mathematically.

quote:

rnb asks for conversion from tons per square inch to psi and that is simply 40,320 psi mathematically.

Wrong. It isn't PSI, nor does it convert to PSI. It's Base Copper Units of Pressure. To refer to it as PSI reflects a failure to understand what is being measured and how, promoting confusion that can potentially be dangerous.
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"Serious rifles have two barrels, everything else just burns gunpowder."

400NE

I am not forming an opinion on what or how something is being measured. I was simply stating the conversion factor as was originally asked. You are probably perfectly correct in your exertion of what and how proof pressure or chamber pressure is measured and I was not clling that into question, in fact I acknowledged that in my post.

There is no getting away from the fact though that if you refer to a measure, no matter how you got it, in tons per square inch then that can be expressed in pounds per square inch which is abbreviated as PSI. No different than 1 square foot is 144 square inches.

I am not trying to confuse but just wished to point out that there is straight mathematical relationships between like units of weight, length etc.

Absolutely agree with you 100% that you need to be careful when trying to work out how chamber pressure has been measured and by whom, e.g I certainly would not convert metric measured pressure into imperial units even though there is a mathematical equivalent, because if then 'comparing' with other pressure data in imperial units there can be big differences in how the pressure was measured in say Europe or England.

In all due respect to your concerns, I still stand by my original assertion that if you give me a figure of 1 ton per square inch and ask me to express it in smaller units, I am quite right in giving you the answer of 2240psi. I would pass an exam with that answer.

quote:

Originally posted by eny:
Is there a good book that has this kind of info? What is a good book about double rifles.

An excellent book about DR is Graeme Wright's
"Shooting the British Double Rifle". It has been published by the Author in 1996.
Graeme Wright, P.O. box 5085, Kenmore East 4069, Australia.
Published by S.S.A.A. Big Game Rifle Club, P. O. box 186, Prahran, Vic 3181, Australia.
I learned a lot about DR, regulating them, DR pressures etc.
Kind regards, Hans

Eagle27,
Perhaps this thread would be helpful?
pressure conversion thread

quote:

Originally posted by HJ wild:

quote:

Originally posted by eny:
Is there a good book that has this kind of info? What is a good book about double rifles.

An excellent book about DR is Graeme Wright's
"Shooting the British Double Rifle". It has been published by the Author in 1996.
Graeme Wright, P.O. box 5085, Kenmore East4069, Australia.
Published by S.S.A.A. Big Game Rifle Club, P.
O. box 186, Prahran, Vic 3181, Australia/
I learned a lot about DR, regulating them, DR pressures etc.
Kind regards, Hans

An excellent read, I highly recommend it.

quote:

Originally posted by eagle27:
400NE

I am not forming an opinion on what or how something is being measured. I was simply stating the conversion factor as was originally asked. You are probably perfectly correct in your exertion of what and how proof pressure or chamber pressure is measured and I was not clling that into question, in fact I acknowledged that in my post.

There is no getting away from the fact though that if you refer to a measure, no matter how you got it, in tons per square inch then that can be expressed in pounds per square inch which is abbreviated as PSI. No different than 1 square foot is 144 square inches.

I am not trying to confuse but just wished to point out that there is straight mathematical relationships between like units of weight, length etc.

Absolutely agree with you 100% that you need to be careful when trying to work out how chamber pressure has been measured and by whom, e.g I certainly would not convert metric measured pressure into imperial units even though there is a mathematical equivalent, because if then 'comparing' with other pressure data in imperial units there can be big differences in how the pressure was measured in say Europe or England.

In all due respect to your concerns, I still stand by my original assertion that if you give me a figure of 1 ton per square inch and ask me to express it in smaller units, I am quite right in giving you the answer of 2240psi. I would pass an exam with that answer.

eagle27:
The original question was:
“How many PSI is a ton of English proof I have tried to find the answer for a double rifle I have the listed proof is 18 ton per square inch how”
I don’t know any one on hear who can’t pass your little test. The test you can’t pass is understanding that PSI and TPI are apples and pears they are not related. You can’t get PSI chamber pressure no matter how you manipulate TPI.
Merry Christmas
Bill

Bill and 400NE, nowhere have I inferred that my expressing tons per square inch in the equivalent of pounds per square inch is the measure of chamber pressure or bolt thrust or CUP or LUP. In fact I have acknowledged so in each of my posts.

I am quite familiar with the different methods of measuring pressure in firearms and while not wishing to be pedantic, I was only pointing out that if someone measures pressure with whatever method (LUP, CUP, etc, etc) and converts that measure and expresses that measure in tons per square inch then it can also be expressed in pounds per square inch.

To simplify this, if a copper or lead crusher disc is placed on a non-compacting surface and a ton weight is placed on that disc, the amount of crush can be measured. If the crusher disc were 1 inch square then the pressure on that crusher disc is 1 ton per square inch. If you had 2240 pounds and also sat it on that same crusher disc you will get exactly the same crush effect.

Therefore aside from how or where the original method of measuring pressure comes from, if the measurer has converted CUP or LUP or whatever into tons per square inch (from crush tables etc) then it is absolutely perfectly legitimate to express that as pounds per square inch.
In the nicest possible way, if that can't be accepted then everything Einstein did was flawed.

Just remembered I have a copy of a letter from Norma to Roger Hale with data on the 404 Jeffery ammunition they loaded for Parker Hale back in the ‘70s (red box with cross hair on elephant head). I had made enquiries from Parker Hale as to the specs of their ammo.

Norma state that the 400gr FMJ round was loaded with 5.65grams or 87 grains N204 powder at a MV of 2245 ft/sec with an average maximum pressure of 2,365 atm. or 34,765 psi (straight mathematical equivalent 15.7psi/atm)

34,765psi expressed as tons per square inch is 15.5 tpi.

The original 404 Jeffery pressure specification for the 400gr loading (probably Kynoch) is usually quoted as 16 tpi.

Norma powder is known for it’s capability of producing good velocity with lower pressures.

Note that Norma is using direct mathematical conversion of like units once they have established the chamber pressure, which I understand back in the 70’s when the letter was written was with CUP. At some stage in their measurements they have established that the units of CUP they obtained from pressure testing their 404 Jeffery ammo was convertible to atmospheres and they were then quite happy to express this directly converted to psi.

I understand that Norma pressure tests with copper or lead crushers used cases with a disc removed from the cartridge wall so that the copper or lead disc was acted on directly by the pressure device piston under chamber pressure and not how in the USA the cartridge case wall was pierced by the chamber pressure. That was one reason why when Norma ammo was pressure testing in the States it always showed higher pressure than that published by Norma. The actual chamber pressure of the cartridges must have been the same but the slight difference in the pressure test device made for different results.

Any way if Norma is happy to express chamber pressure in atm or the direct mathematical equivalent in psi which if converted to tpi is almost identical to the English originated specification for the cartridge, then gee wiz who am I to argue. I’ll argue my case with others but sorry not Norma.

quote:

nowhere have I inferred that my expressing tons per square inch in the equivalent of pounds per square inch is the measure of chamber pressure or bolt thrust or CUP or LUP. In fact I have acknowledged so in each of my posts.

Whew, glad we cleared that up!

Thanks Rusty and I did read the thread you indicated.
On re-reading my last post referring to the letter from Norma, I perhaps may have left that open to confusion. I should have quotationed the sentence as that is the exact words as written from Harald Bergh of Norma. I have only added the comment in brackets.

I do note that the modern Kynoch ammunition loaded for the 404 Jeffery is at a published pressure of 16 tons per square inch at 15C temperature.