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Double Rifles, Single Shots & Combinations >> Building Double Rifles & Gunsmithing

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oupa
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Proof... once again
#170364 - 27/10/10 09:50 AM

While this subject is often discussed in regards to the states where we have no official or easily accessable "proof house" the norm or at least that arguably "established" by way of Brown's book is a 30% over load of some sort. I will not go into that debate right now but as this is the first such project I've done since reading it way back when, I was wondering how you guys view the method our own Bramble encountered at the London proof house. That being, simply oiling a pair of heavy (but within spec.) cartridges. I for one am certianly not going to argue with such experts but am curious if others have tryed it. Here's an excerpt from that post with emphisis added;

"...It was an interesting experience. The test itself consisting of taking two of my heavy crimp maximum reloads and librially oiling the cartridges and firing them in a test room that resembles the entrence to Dantes inferno with a huge ammount of powder residue on everything. A nicer bunch of people you could not hope to meet by the way, they let me observe all that was going on and made me a cup of tea to drink whilst wandering around their workshop.
They also decided that the test was sufficient for definitive proof and that I did not need to return the rifle after the ribs were added.

I enquired of course just what additional strain the oiling of the cartridges puts on the action and I was assured that it was in excess of 30%. I was told with some undisguised pride that the same proceedure had recently pushed a .600 by a well known manufacturer off the face. This was before they fired my humble effort (gulp). The excess pressure produced was sufficient to force the primers to extrude into the firing pin holes 0.0085" to the extent that a burr could be removed from the primer with a fingernail on examination."

And a link to the whole thread; http://forums.nitroexpress.com/showflat.php?Cat=0&Number=69065&page=0&fpart=1&vc=1

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4seventy
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Re: Proof... once again [Re: oupa]
#170376 - 27/10/10 03:41 PM

oupa,
I think it is astonishing that the London Proof House would claim to have "proofed" a rifle in such a ridiculous manner.
Seeing that they had no idea what pressure Bramble's cartridge was producing, they also have no idea what pressure their "proofing" was done at.
In reality they proved the rifle at "no idea plus 30%"!
The plus 30% was a guesstimation by the proof house as well,(edited to add) and is incorrect IMO.

Edited by 4seventy (27/10/10 09:17 PM)

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kamilaroi
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Re: Proof... once again [Re: 4seventy]
#170381 - 27/10/10 06:58 PM

I understand that there used to be a "blue pill" load but it may be that Thatcherite etc economics has retired that standard of proof.

Comments?

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oupa
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Re: Proof... once again [Re: kamilaroi]
#170396 - 28/10/10 03:26 AM

My point in asking is that in absence of some rather expensive equipment and expertise that is not readily available outside "the factories" here in the states, any means of "proofing" a home built gun is essentially conjecture. We can add so much powder to the load or a bullet heavier by a certian percentage but without scientific measurement tools we're still only guessing. I'm I wrong?
However if this method, as crude as it seems has been deemed adequate by such a prestigeous establishment... well you get the picture right? It would seem so much simpler than some mystery load who's actual pressure would still be just as much conjecture as the oiled cartridges.

The project I'm working on presently is a .30-30 on a Belgium marked 12 bore hammer gun. I'm at the testing stage and thought I'd give this method a try unless there was any actual negative experience with it by the other members.

4seventy, I respect your opinion and totally agree. However as they've been doing this (proofing) for centuries, most of the time governed by extensive previous experience rather than scientific measurement, I'm inclined to defer to thir methods. After all, many of the prectices in building a double gun or rifle are more "experience" than science. Why should this be any different?

I haven't visited the forum for a while until recently and would love to have Bramble chime in on this. Perhaps a PM is in order...

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DarylS
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Re: Proof... once again [Re: oupa]
#170399 - 28/10/10 03:57 AM

4seventy's right - no regulation worth while on that proof.

Oiling the brass certainly increases the strain on the breech - but it is not definitve - ie; cannot be controled to produce a repeatable result.
things that change the pressure against the breech: here's some things that change the breech thrust, off the top of my head.
1/. shape of ctg. ie: taper
2/. condition of ctg brass - ie: temper/smooth/rough
3/. viscocity of the oil
4/. amount of oil
5/. lubricity of oil
6/. powder charge and bullet weight of load

I frequently oil ctgs. when firforming. I use a thin oil, like WD40, which has lower lubricity in comparrison to other oils of the same viscocity, even. The incrase in bolt thrust cannot be felt in extraction, buy allows better case forming.

'lots' of oil - a non-compressible liquid - lots? Good grief - are they wishing to ring the chamber?

--------------------
Daryl

"a gun without hammers is like a Spaniel without ears" King George V

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kuduae
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Re: Proof... once again [Re: DarylS]
#170426 - 28/10/10 06:13 AM

imho the people at the London proofhouse did know pretty well what they were doing! Since 1895 the Brits used the "Woolwich" or "oiled case system" to determine their "tons per square inch" pressures. In the April 1967 issue of THE AMERICAN RIFLEMAN Roy G. Goodman described this system. The pics are from this article just to save them. Instead of bleeding off some gas through a hole in the barrel to a piston , which in turn deforms a copper crusher (cup) or works on an electronic transducer, the Brits used the cartridge case as the piston. The case worked on a moveable breech, which rested on a copper crusher.

Tons per square inch were then calculated from the force needed to deform the crusher and the base area of the case. The photo shows the "bolthead", the breechblock and crushers new and deformed by various grades of pressure.

The Woolwich system required an oiled cartridge case to preclude friction between cartridge and chamber walls. Using a case and chamber free of oil only gave about two thirds of the "true" pressure readouts. If the case was oiled, case shape had no influence on breech pressure! The pic shows the breechblock and a can of oil in front of the pressure test gun.

The military proof of .303 Lee-Enfields consisted of firing one "blue pill" proofload and one service load with an oiled case. Rifles that stood the proofcharge sometimes failed on the oiled service cartridge. So I think the guys at the London proofhouse know much more about pressures, case shape and oil viscosity than other members of this forum.
BTW, German proofhouses without a proper proof cartridge in a pinch simply heated a service cartridge to 80 degrees Celsius and used this as a "proofload".
2nd BTW, due to even more inertia the Woolwich system gives only about 80% of the pressure readout of the Rodman copper crusher (cup) system. So it is not possible to simply convert "tons per square inch" to cup or psi or bar using a pocket calculator!

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Edited by CptCurl (29/10/10 03:27 AM)

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kuduae
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Re: Proof... once again [Re: kuduae]
#170434 - 28/10/10 06:49 AM

3rd BTW: Those old British experiences with oiled cartridges and/or chambers should be a warning against using high-pressure, straight-walled cartridges like Weatherby's or RUMs from oily chambers. It is a well-known fact here that rear-locking bolt rifles like the Steyr-Mannlichers or the Sauer&Sohn 80-90 series, as well as many break-open rifles, will change point-of-impact considerably if oil is left in the chamber. The different case set back will upset vibrations.

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Huvius
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Re: Proof... once again [Re: kuduae]
#170435 - 28/10/10 07:36 AM

The photograph above, IMO, is only to demonstrate the breech force/pressure of a factory loaded cartridge ie. the Kynoch ammo in the picture.
The copper crusher has no correlation at all to the proof of a finished rifle other than establishing a baseline pressure for a specific factory loaded cartridge. I guess what I am saying is that it is for testing ammunition not proving a firearm.

Some proofing was apparently done using an overweight bullet with a standard service charge of powder in a specific rifle. This makes sense in a double which is regulated for a specific bullet weight and powder charge which will not be deviated from.

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kuduae
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Re: Proof... once again [Re: Huvius]
#170439 - 28/10/10 08:10 AM

Huvius, of course this system was used to test ammo,not rifles. I posted this stuff just to show that the British proofhouses, who also pressure tested ammunition to find the proper proof loads, have a lot of experience with the relations of cases, oil and breech pressures. In the example cited by oupa above, the proofmasters were quite sure the barrels would hold the pressure, but tested the breeching of the rifle. They did not just smear some old oil on the cases. They simply knew from their experince with the ammo testing gun that using the Woolwich system's oil on the cases would increase the pressure on the breech by "at least 30%". And , be assured, European proofmasters have some leeway: If they are sure a gun is safe with the prescribed loads, they let it pass, if not, they will reject it. After firing a "blue pill" load (an American expression, as .30-06 military proofloads had a blue primer), they are to inspect a gun for defects, fi has it gone off face. If a break-open has opened the slightest amount, it will be rejected.

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4seventy
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Re: Proof... once again [Re: Huvius]
#170444 - 28/10/10 08:33 AM

Quote:

The photograph above, IMO, is only to demonstrate the breech force/pressure of a factory loaded cartridge ie. the Kynoch ammo in the picture.
The copper crusher has no correlation at all to the proof of a finished rifle other than establishing a baseline pressure for a specific factory loaded cartridge. I guess what I am saying is that it is for testing ammunition not proving a firearm.

The above quote is absolutely true.

This is what gun proof is supposed to achieve and how it should be done.....

>>>involve the firing through the barrel of a considerably heavier load than is customary in the shooting field, thereby setting up pressure and stress on barrel and action much in excess of the pressure generated by standard load cartridges. Such pressure should, and is intended to, disclose weakness in guns, whether new or used, for it is preferable that weakness be found at a Proof House rather than in the field, where personal injury may result.<<<

You can throw oil on a (standard pressure) cartridge case all day and all night, and it will never change the pressure of that cartridge. All that the "oiling" achieves is to reduce the grip of the brass case against the chamber wall.
Therefore the barrel and chamber is not being subjected to any more pressure than with a dry case, and this means that the barrel and chamber has not been subjected to any "proofing" whatsoever.

Also, the (standard pressure) "oiled" case, with it's reduced grip against the chamber wall, will not put any more stress on the breeching than what a (standard pressure) case head separation will produce.

The proofing done in the manner in which Bramble's gun was done, does nothing as far as testing the gun "above" whatever pressure Bramble's hunting load produced.

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kuduae
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Re: Proof... once again [Re: kuduae]
#170445 - 28/10/10 08:43 AM

European proofhouses don't test guns only, they are constantly testing ammunition too. Before an ammunition manufacturer or importer releases a new batch of ammo, he has to send samples to the proofhouse. There it is pressure tested. If it is not within the maximum pressure established for that cartridge, it cannot be sold to the public. So some American factory loads are not available in Europe, because they exceed CIP pressure limits. Often this prescribed testing is not worthwhile for the importers, because the small numbers that may be sold don't justify the expenses to have the ammo tested and approved. Further, if an ammo maker changes any component, the new lot has to be reprooved.

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4seventy
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Re: Proof... once again [Re: kuduae]
#170457 - 28/10/10 12:58 PM

Quote:

They simply knew from their experince with the ammo testing gun that using the Woolwich system's oil on the cases would increase the pressure on the breech by "at least 30%".

Increase the pressure on the breech by at least 30% of what?
In this case a handloaded hunting cartridge, supplied by the owner of the firearm, the pressure of which is unknown!

If that handload was producing less than the MAP for that particular cartridge, then the 30% oiled case increase on the breech thrust may not even be enough to equal the breech thrust of an un-oiled factory loaded round!

What they did has little or nothing to do with gunproof, nor did they adhere to the rules laid down for British gun proofing.
They then stamped the gun as being safe for a certain pressure, when they didn't have the faintest idea what pressure they had used during the "proofing".

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DarylS
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Re: Proof... once again [Re: 4seventy]
#170503 - 29/10/10 03:30 AM

I concede to the British "Oiled ctg" Woolwich testing of breech thrust, which was done in a controlled (fairly) environment, but it does nothing to test the barrel & chamber.

Considering that testing the action was the primary goal, perhaps it's just fine - however the question of loads and what load was used is also important in the equation. One man's maximum load is sometimes not equal to what a maximum load actually is - not suggesting Bramble loads lightly - but - perhaps it's all relevent, perhaps not.

I'm not sure I'd want my actions submitted to 'over 30%' more pressure than they will ever experience - in reality, my improved ctg. actions experience very little pressure - virtually. Does this 'stree' the action for future failure? If oiling a tapered round produces the same pressure increase as oiling an improved ctg. then the increase in pressure against my actions would probably be over 100% of normal - something they will never experience and have no need to.

I guess it works for them, the actions of the DR's being the weakest part of the gun.

--------------------
Daryl

"a gun without hammers is like a Spaniel without ears" King George V

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oupa
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Re: Proof... once again [Re: 4seventy]
#170505 - 29/10/10 03:31 AM

While 4seventy and those similar opinions are all valid I think the discussion is straying slightly from my original point... That being that here in the states where a government proof house is not available and private "proofing" is cost prohibitive various means of "proofing" homebuilt guns are employed, or in many cases I'm sure, skipped over. That said, kuduae's excelent explaination I think nails the delima! Yes, the Woolwich method (which I'd never known of before) is for testing ammo it seems. That it has scientificly established that the pressure forces of any ammo can be expected to increase by the target 30% is the key to the issue.
Yes 4seventy is correct that it is 30% of an unknown but then in this particular situation it is "unknown" anyway so any attempts to increase it by any factor are also "unknown!" Increasing bullet weight or powder charge in the absence of expensive equipment and the expertise to use and interpret the results is merely conjecture and could be spot on or very far off.
This more or less proven method of increasing even an "unknown" pressure by roughly 30% should be useful in my opinion. Where this really shines is as someone else mentioned I think, that a double rifle is regulated to a particular load. If THAT load can be increased by roughly 30% by this method we at least have a reference even in the absence of knowing it's actual pressure either oiled or dry! That is the objective isn't it?

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kuduae
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Re: Proof... once again [Re: oupa]
#170518 - 29/10/10 07:39 AM

Quote:

Considering that testing the action was the primary goal, perhaps it's just fine - however the question of loads and what load was used is also important in the equation. One man's maximum load is sometimes not equal to what a maximum load actually is - not suggesting Bramble loads lightly - but - perhaps it's all relevent, perhaps not.

European proof rules told most of the time: The man submitting a gun for proof has to tell the cartridge for which the gun is to be proofed. If it is a factory chambering, maximum pressure of the service load is determined by the CIP tables, and so is the proofload with 30% more pressure than the service load maximum. At least in Germany, the 1940 proof rule prescribed the maximum pressure of the highest pressure German factory load then available to be the max service cartridge pressure, hence the ridiculously low max pressures of some old cartridges like the 9.5x57M-Sch. But there always was an exception: For cartridges with no standard factory loads available, the maker has to describe exactly the load for which the gun is to be proofed and has to send in at least six such loads and components, perhaps even his reloading tools, with the gun. Then the gun is proofed for this load alone. Loading ammo with a higher pressure than the load submitted for proof is illegal. Remember, proof is meant to determine if a gun is safe using factory cartridges, many handloading "recipes" make the gun "out of proof" for this load and the user is on his own, without the slightest chance to sue anyone.

Quote:

I'm not sure I'd want my actions submitted to 'over 30%' more pressure than they will ever experience - in reality, my improved ctg. actions experience very little pressure - virtually. Does this 'stree' the action for future failure? If oiling a tapered round produces the same pressure increase as oiling an improved ctg. then the increase in pressure against my actions would probably be over 100% of normal - something they will never experience and have no need to.

Proof rules simply require a 30% higher pressure than the service load! If your gun shows any defect such as bolt setback or gaping, it is to be rejected. This indeed troubles the proofhouses with some new American high-intensity cartridges, as their service pressure is already so high that the prescribed 30% increase makes brass "flow" like a liquid and makes properproofing impossible.

BTW, how do you know your "improved" cartridges give such a low back pressure? Have you really measured anything under controlled conditions or are you merely guessing too? How do you arrive at a 100% increase? British experience simply state "more than 30%, likely 50%".

Quote:

I guess it works for them, the actions of the DR's being the weakest part of the gun.

I agree here!

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kuduae
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Re: Proof... once again [Re: 4seventy]
#170520 - 29/10/10 07:46 AM

Quote:

Also, the (standard pressure) "oiled" case, with it's reduced grip against the chamber wall, will not put any more stress on the breeching than what a (standard pressure) case head separation will produce.

Only if you manage to load an already seperated case! The force needed to tear the case apart can not work on the breech anymore!

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4seventy
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Re: Proof... once again [Re: kuduae]
#170521 - 29/10/10 08:26 AM

Quote:

Quote:

Also, the (standard pressure) "oiled" case, with it's reduced grip against the chamber wall, will not put any more stress on the breeching than what a (standard pressure) case head separation will produce.

Only if you manage to load an already seperated case! The force needed to tear the case apart can not work on the breech anymore!

That's not correct when dealing with some double rifles.
For example, owners of 9.3x74R doubles, who reload Norma cases, often complain about case head separations on just the second or third firing of a reloaded case. This is with standard pressure reloads, and it happens often, due to the extremely thin case walls of Norma brass.
In those instances of head separation, the case is already partially separated on the first firing, and on just the second firing the breech will need to endure the full thrust, which is at least equal to, and probably more than what would happen with an oiled case.

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4seventy
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Re: Proof... once again [Re: 4seventy]
#170522 - 29/10/10 08:45 AM

The rules laid down for British gun proof stipulate that the following must be done.

"the firing through the barrel of a considerably heavier load than is customary in the shooting field"

That was NOT done. It really is as simple as that.

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DarylS
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Re: Proof... once again [Re: 4seventy]
#170526 - 29/10/10 10:21 AM

Proofing became very arduous indeed, when black powder was replaced with smokeless powder. With black powder, the charge could be increased by 20, 30, or 100%, but doing so with smokeless powders resulted in dismemberment for the gun itself. It appears the 'oiled' case was an effort to standardize and reduce the pressure excursions that happen with smokeless, especially the smokeless powders of 1900 through the 40's.

As to my guess on 100% more breech thrust when oiled, compared to a normal dry load, the 100% was just a guess, just as the proof house's guess at something over 30% for tapered case that's oiled.

That the straightened, minimal taper case shows little to no breech thrust is well known by anyone who has loaded extensively for these Improved cases. The straighter and longer the case, the lower the thrust. Our .375's have only .005" taper per size - only 75% taper of a 'normal' Improved case, which is about .0075" per size. How do I know the straight case developes so much less thrust - I know as everyone who has been a wildcat shooter for 30 years knows - through experience. I suspect you are not familiar with loading for Ackley Improved rounds.

--------------------
Daryl

"a gun without hammers is like a Spaniel without ears" King George V

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Birdhunter50
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Re: Proof... once again [Re: oupa]
#170551 - 29/10/10 11:41 PM

Why mess around with oiled cases at all? There is too much probablity of differences in achieved pressure, and as stated, that method does nothing to proof test the barrels. I would recommend picking the highest pressure load for your particular caliber and then simply use a 30% heavier bullet with the same powder charge. This method is KNOWN to increase the pressue by the same amount as the increase in bullet weight above the normal weight. It is predictable and repeatable, and it is a good test of the whole system of the gun. There are too many variables in oiled cases and it is an incomplete proof test as well. Bob H.

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Mike_Bailey
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Re: Proof... once again [Re: Birdhunter50]
#170554 - 30/10/10 12:51 AM

Kuduae, I thought it was 50% ?, best, Mike

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DarylS
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Re: Proof... once again [Re: Mike_Bailey]
#170555 - 30/10/10 01:35 AM

statement is over 30% - at least 30% - Kuduae guessed it might be as high as 50%.
Probably ranges that much, case to case due to taper and chamber conditions.
A chamber that is rougher- ie: reamed but not polished, which is normal, will produce less pressure than one that is polished. Then come pits in old guns being re-proofed - I firmly believe there are too many variables in merely oiling cases, even if the same oil is used. Of course, they are using a copper crusher, so get pressure readings each shot when testing the load in the crusher apparatus- must remember that. However, they are then oiling the ctg. case and putting it into a different chamber and fireing it, along with the possibly different conditions, which also includes different dimensions of chamber body, leade and throat diameters and lengths.

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Daryl

"a gun without hammers is like a Spaniel without ears" King George V

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GroovyMike
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Re: Proof... once again [Re: DarylS]
#170557 - 30/10/10 02:10 AM

I am showing my ignorance here but am I correct in understanding the above as claiming that oil on your cartridge case increases the pressure of the load? This seems counter intuitive. If the powder and projectile is unchanged how is the pressure increased? Is it because the oil reduces chamber size some tiny bit, or because the brass fails to grip the chamber walls and so puts more pressure on the bolt face? Have I missed the point entirely?

Am I increasing my load pressure by 30% by leaving case lube on my cartridge cases?

--------------------
Delight yourself in the Lord and He will give you the desires of your heart. Psalm 37:4

Edited by GroovyMike (30/10/10 06:26 AM)

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450_366
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Re: Proof... once again [Re: GroovyMike]
#170559 - 30/10/10 03:04 AM

Doesent oil under high pressure combust/detonate?

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Andreas

"Yeas it kicks like a mule he said, but always remember that its much worse standing on the other end"

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oupa
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Re: Proof... once again [Re: 450_366]
#170564 - 30/10/10 04:39 AM

450 366, Yes. It is called the diesel effect and is the principal behind the deisel engine... an oversimplification perhaps??? A good point though just the same!

GroovyMike, The principal as I understand it at least is the reduction or even elimination of friction / grab of the cartridge on the walls of the chamber thus placing the full force of the rebounding action of the (fired) cartridge fully on the breech face instead of disipating some of that force through adhesion to the chamber walls.

To all,
Geeeeez! I only intended to ask if anyone had tried this method or if they considered it worthwhile. Never imagined it would turn into such a debate but I'm kind of glad it did. Maybe this is something that needed some fleshing out.

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