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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Wed Aug 06, 2014 2:06 pm 
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Sept. 10, 1904 Sporting Life “Burst Gun Barrels”
http://library.la84.org/SportsLibrary/S ... 326021.pdf
The number of burst gun-barrels which, comes to the attention of the shooting public is remarkably small, considering the thousands of guns in use throughout the country. The main reason for the comparatively small number of guns burst is the great use of factory-loaded shells, or the hand-loaded of reliable dealers. The day of loading one’s own shells is pretty well passed, therefore, the over-loaded or double-charged cartridge is very seldom found. Very often a burst barrel is blamed on the gunmaker or the shell-maker, but more often on the manufacturer of the powder. Cases are known where a party blowing out a gun-barrel, using an extra heavy charge of dense powder, blamed it on a bulk powder. A suit for damages was quickly withdrawn after an examination of the gun had been made.


A 3 Dr. Eq. (Dram Equivalent) load of “E.C.” No. 1 or “Schultze” was 42 grains by weight. 3 Dr. Eq. of Dense Smokeless Ballistite was 24 grains; Infallible 21 grains. The pressure of a 3 Dram (82 grains by volume) load of Black Powder propelling 1 1/8 oz. of shot at 1200 fps is about 5000 psi. The pressure of 1 1/8 oz. 3 Dr. Eq. of BULK Smokeless was 6500 - 7500 psi; 3 Dr. Eq. of DENSE Smokeless was 9000 - 10,000 psi.
Substituting a Dense Smokeless powder for Black or Bulk Smokeless powder would double the charge. It has been estimated that 50 grains of Infallible (later Unique) could reach 30,000 psi. Combine this error with a 3” shell in a 2 5/8” or 2 1/2” chamber, and a barrel rupture might occur in any barrel, fluid steel or Pattern Welded.

Sears, Roebuck & Co. Catalogue No. 116 1907 courtesy of Gary Rennles
"When a gun barrel bursts at the breech or chamber it is caused by an overload of nitro powder, and when it bursts forward of the chamber it is caused by some obstruction..."
“Nitro powder should only be used by people familiar with it; and dense nitro powder should be weighed by an apothecary’s scale and not measured.”

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Lots of infro here
https://docs.google.com/document/d/1F2s ... FU/preview



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Richard Baxter (1615-1691), Directions Against Covetousness
"Be more careful to use what you have, than to get more."

Kingsley Brown "Shoot more, shop less."


Last edited by Drew Hause on Wed Aug 17, 2016 7:38 pm, edited 7 times in total.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Tue Oct 07, 2014 3:56 pm 
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Drew:

I suspect you may be misleading some readers on the inherent safety of vintage (Circa 1900 or before) shotguns while minimizing the risks of handloading shotshells.

Accidental handloads with double, or even triple, charges of powder are known to destroy shotguns barrels. Even overloads of shot or incorrect primers may cause failures. I suspect that commercial shotshell manufacturers use various double checks of their loads while most handloaders ignore them.

I’m aware of no instances of catastrophic failures when firing safely loaded shells. To the contrary, misloaded shells can blow any gun, old or new. I have seen many pictures of failures that were attributed to misloads or plugs. If a cause was given for the failure none were attributed to weak barrels. The pictures you show include newer guns and guns blown by misloads. I didn’t see one attributed to old weak barrels.

Sherman Bell performed the only comprehensive tests on the safety of vintage shotguns that I am aware of. He collected 30 old 12 Ga. wallhangers: Fluid Steel and Damascus barrels, American and Belgium made. They had numerous flaws such as corrosion, severely honed barrels, bulges and dents. Many were ‘low quality’ inexpensive Belgium guns or guns sold by Sears.

He subjected each gun to modern Proof Pressure firings of 18,500 PSI. All guns past these Proof tests with no bursts or bulging. He subjected two guns, one each with Steel and Damascus barrels, to increasing pressure until they burst. Both failed at about 30,000 PSI, almost 3x the maximum recommended 12 Ga pressure of 11,500 PSI.

A Metallurgist subjected the purposely blown guns to a detailed analysis. There were no indications of any of the corrosion extended internally to weaken either gun. There was no indication of any weakness in the welds of the corroded Damascus barrels.

Sherman had one guns’ barrels machined out to 0.783” (technically 10 Ga bores) to a 0.046” wall thicknesses (about ½ the original) at 6” from the breech. It was still of marginal strength at Proof pressures: one barrel bulged on the first firing and then blew on the second while the other survived ten proof loads. BTW: over ½ Lbs. of metal had to be removed, way more than required to polish a bore.

The European minimum wall thickness standard can be seen at http://www.cip-bobp.org/sites/default/f ... 4-1_EN.pdf. It calls for a minimum thickness of 0.075” at 3.9” from the breech end of the barrel (about 1” in front of the cone) for low tensile strength steels. This appears to be consistent with the machined 0.046” wall being of marginal strength at Proof pressures.

One of the tested Twist/Damascus guns’ barrels had previously been bored from the nominal .730” of a 12 Ga to .760” right and .764” left, leaving the barrels about 0.030" thinner than original and it still passed Proof pressures.

Sherman also performed tests to confirm the causes of failures of the shotguns (new or old). A double charge of a fast powder caused a violent failure at the breech end of a gun. Solid plugs caused failures near the plug.

His test guns had various loose and damaged parts including loose lockups. These flaws worsened when fired at Proof pressures while strapped in a cradle. There were no indications that these flaws presented safety problems; the barrels are the only pressure containing parts of a gun.

More details of Shermans’ tests can be found at: viewtopic.php?f=13&t=259371&start=40 about 1/3 down the page.

I believe that inconsistencies in the manufacture of Nitro Powders, inaccurate loading information and the lack of proper loading equipment were the main causes of shotgun failure at the time, not weak guns.

Bob


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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Tue Oct 07, 2014 5:56 pm 
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Hunter Arms would agree Bob

Notice “All our guns are tested with heavy loads and cannot burst except by carelessness, obstruction in the barrel or improper home loaded shells with nitro or dense powder.”

Image


Thoughts regarding wall thickness

The Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives (C.I.P) minimum wall thickness recommendations for ‘Standard Steel’, defined as a tensile strength 101,500 - 123,000 psi:

For 12g Standard Steel...................................................20g

End of chamber - .079”....................................................075”
Just past the forcing cone/ 4” from breech - .075”...................071”
8” - .043”....................................................................041”
12” - .030”...................................................................028”
16” - .024”...................................................................022”
20” - .022”...................................................................020”

2.The average tensile strength of both Crolle Damascus and Twist is about 54,000, a bit less than Decarbonized or Siemens steel. There was however only a slight difference in the performance of pattern welded vs. late 1880s steel barrels in the Birmingham Proof House Trial
http://docs.google.com/a/damascusknowle ... edit?pli=1

3.Higher tensile strength fluid steel was developed rapidly after 1890.
Krupp Nickel Steel patented in 1890: 92,500 psi
Winchester Nickel Steel, introduced about 1896: 100,000 psi
Remington Ordnance Steel, introduced in 1897: 110,000 psi
ONE sample of Hunter Arms Co. Armor steel, introduced in 1898: 101,000 psi
1905 Krupp Chrome Nickel Steel D: 106,500 psi
Marlin “Special Smokeless Steel” introduced for the Model 1893 rifle in 1897 and Model 21 Grade C Pump in 1907: 100,000 psi

4.In 1918, Sears advertised the Fulton/Gladiator barrels as having a tensile strength of 85,000 – 95,000 psi.
The ‘LLH’ mark of Laurent Lochet-Habran is frequently found on L.C. Smith Royal, Armor, London, Crown and even Nitro Steel barrels from 1914 to 1948, Hunter Arms Fulton, Gladiator and Ranger for Sears, and also Fox, Ithaca, Lefever, and Baker guns.
This figure may therefore reflect the strength of the post-1900 Belgian ‘rough forged tubes’ used by most U.S. makers.

5. The industry standard for modern AISI 4140 Chrome Moly gun barrel steel is 95,000-100,000 psi.

Recommendation:

I would not shoot any barrel that is deeply pitted and has a wall thickness less than .020" in the distal 1/3 of the barrel because one cannot know the wall thickness at the bottom of those pits.

Every vintage shotgun, and shotgun barrel, should be evaluated before use by someone with the equipment and expertise to properly do so, and then shot only using ammunition with ballistics similar to that for which the gun was originally intended.


Evaluation recommendations
https://docs.google.com/a/damascusknowl ... c-kGA/edit

More information may also be found here
http://docs.google.com/a/damascusknowle ... edit?pli=1

_________________
http://sites.google.com/a/damascusknowl ... m/www/home

Richard Baxter (1615-1691), Directions Against Covetousness
"Be more careful to use what you have, than to get more."

Kingsley Brown "Shoot more, shop less."


Last edited by Drew Hause on Sat Jan 09, 2016 4:38 pm, edited 2 times in total.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Wed Oct 08, 2014 12:11 am 
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Drew:

I had no intentions of questioning your suggested wall thicknesses. I was merely pointing out that Sherman Bell’s failure tests on vintage thinned barrels were consistent with modern recommendations.

Sherman didn’t report original walls thicknesses on the guns he tested, if I remember correctly, and I haven’t been able to find any significant data on it. I assume the walls were often thicker than required by modern recommendations so that any barrels made of the lower tensile strength steels could pass Proofing pressures.

Since you have measured the wall thicknesses on many vintage shotguns (or have had them measured?) I am wondering if you could share the thickness results with us. Were there any indications that the barrels had been thinned internally or externally? Did you measure wall thicknesses on any blown barrels to confirm they were too thin?

Did you find any vintage barrels made of higher strength steels? I believe high strength steels had long been used in heavily loaded applications needing wear resistance like tool steels.

Alloy Steels were new at the time but they weren’t the only method of gaining strength. Increasing Carbon content, quenching, annealing and work hardening were all well-known at the time. (Hardness tests are an easy way to estimate strength if anyone is curious; the higher the strength the harder the steel.) Names like Armour Steel and Ordnance Steel were only sales hype as far as I can determine.

You stress that “then shot only using ammunition with ballistics similar to that for which the gun was originally intended”. The only information that I have been able to find suggests that the pressures, loadings and velocities of centerfire shotshells haven’t changed significantly since they were invented in the mid 1800’s.

Actually I don’t see the need to know the ballistics of the typical ammunition of the time. Shermans’ Proof Pressure testing showed that vintage shotguns, regardless of their make or ‘quality’, were capable of holding up to modern pressures and higher, even with flaws. Nothing else is important.

I must admit that I am a bit confused about your statement that ”I would not shoot any barrel, pattern welded or fluid steel, that is deeply pitted and has a wall thickness less than .020" in the distal 1/3 of the barrel because one cannot know the wall thickness at the bottom of those pits.“ How would you know if it is deeply pitted if you can’t measure the depth of the pits?


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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Wed Oct 08, 2014 9:27 am 
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From the Barrel Evaluation Recommendations linked above

Bore inspection
"Inspect bore for pits using a direct or fiberoptic borescope."

Image

Turn-of-the-century barrel strength is discussed in detail here. I only know what I read, or at least what folks claimed :)

https://docs.google.com/a/damascusknowl ... tPYVA/edit

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Richard Baxter (1615-1691), Directions Against Covetousness
"Be more careful to use what you have, than to get more."

Kingsley Brown "Shoot more, shop less."


Last edited by Drew Hause on Wed Jul 15, 2015 3:05 pm, edited 3 times in total.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Wed Oct 08, 2014 11:21 am 
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I don't see any pits. They are dents from some sort of physical damage. Possibly from one of the rotating bore hones with ball shaped abrasive heads gone wild. The raised edge on the one dent with enough light and shadow to see clearly is a dead giveaway. It was formed from metal that was displaced into the bore when the dent was made.

It should be relatively easy to estimate their depth by running a dental pick over them. The bottom of the dents is clearly shown. I doubt if they are much more than several thousandths deep; not enough to affect strength.

Pits have a very small diameter usually like pin points and can be fairly deep. The pictured dents look to be about 1/8” in diameter and are shallow.

At: http://www.doublegunshop.com/forums/ubb ... 668&page=5
You posted pictures of cut-off sections of vintage barrels; Damascus and Steel. You state there is no “orange lace” referring to the color and pattern that could be seen on the newly exposed surfaces of the Damascus if it were internally rusted.

A few pages later on: http://www.doublegunshop.com/forums/ubb ... 668&page=7
You stated:
“RESULTS ARE IN! And many thanks again to all who donated barrel segments, esp. Dennis Potter. I'm saving some of the good stuff for the article but:
1. The findings were remarkably consistent
After discarding the highest and lowest mean:
Twist - 53,300 psi
Crolle - 54,500 psi

2. Four 125 year old samples, Twist and Damascus Twist - 51,500 psi. I guess the mythical delaminating, rusting welds and voids don't really weaken Pattern Welded barrels over time smile

3. As Steve Culver predicted, the JABC Twist barrels were just as strong as the crolle samples.”

Why are you claiming on this site that rusting welds, voids and pitting occur in Damascus types of steel while stating, along with pictures, on another site that they do not occur?

BTW: I hate to burst your bubble but the lack of internal rusting in Damascus was already reported by Xircon (sp?) who analyzed the barrels purposely blown up by Sherman Bell. Sherman reported that JABC barrels are as strong as any other Damascus barrels; they were probably all made in Belgium and all passed their Proofing standards.

I’m beginning to think that this Sticky thread should be unstuck and trashed before it misleads more people.


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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Wed Oct 08, 2014 11:38 am 
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Drew:

You refer to steel tensile strengths covering roughly a 2 to 1 range, from 54,000 psi for the Damascus types up to 110,000 psi for Remington Ordnance Steel; a reasonable range for the time. The higher strength steels would require about ½ the wall thicknesses of the lower strength steels to resist the same pressures.

For example, the European Standards recommend a thickness of 0.075” in front of the chamber for steel strengths in the 110,000 psi range and a thickness of 0.040” for steel strength in the 175,000 psi range. (These standards don’t cover steels with strengths in the 50,000 range. See http://www.cip-bobp.org/sites/default/f ... 4-1_EN.pdf for the details.

The strengths you quote would equate to a thickness in front of the chamber of 0.150” for the low strength the Damascus steels and 0.075” for the higher strength steel. Your recommended minimum wall thicknesses do not specify which strengths of steel they apply to. If your recommendation of 0.105” in front of the chambers were followed the Damascus guns would be fired even though they would be unsafe according to the European standards and higher strength steel barrels would be tossed out even though they are more than safe.

How did you arrive at your recommendations without considering the steels strength? Is an average value close enough despite your dire warnings about flying shrapnel, damaged brains and law suits?


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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Wed Oct 08, 2014 11:55 am 
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You are mistaken. Some of the bore defects are pits, some are machine marks from an unfortunate attempt to length a 16g forcing cone, and what you call dent's are small bulges possibly from a pilot centering the reamer.

External barrel surface at the same point

Image

Not sure of your agenda Bob. I have read the full Metallurgical Failure Analysis of the Bell/Armbrust Parker Barrels that 'Zircon' submitted to the PGCA, not just the partial report that you have cited previously.

By profession and calling I've seen way too much pain and suffering, death and dying to float on any bubbles as meaningless as a study of Pattern Welded barrels.

To clarify the issue of barrel strength and wall thickness, tensile strength is only a part of the equation for estimating bursting pressure. If the barrel is made of Twist with a 50,000 psi tensile strength, that does NOT mean that it will withstand a 10,000 psi load by a factor of 5.

Barlow's formula P=2 S t / D
P=Bursting pressure in psi.
S=Tensile strength of material in tube wall.
t=Wall thickness in inches.
D=Outside diameter in inches.

Barlow’s refers to a pipe capped at both ends with a static pressure (a pressure cylinder). Shotgun barrels are not designed to be pressure vessels as one end is open and the pressure rises and falls quickly.

The Hoop Stress Formula doesn't reliably predict shotgun barrel failure either
http://www.engineersedge.com/material_s ... stress.htm
Shotgun barrels are “thin wall cylinders”
σ = pr/t
p= pressure; r is the inside radius; t is the wall thickness

Wallace H. Coxe, in "Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics" published by E.I. du Pont de Nemours & Co. in 1931 cites a study in which a fluid steel barrel was cut to 9” and capped, then a series of progressively increasing pressure loads fired. The barrel cap was blown off and barrel burst at 5,600 psi.


I would be happy to further debate Pattern Welded barrels if you would please:
1. Read everything on my website. Scroll down to Table of Contents here
https://sites.google.com/a/damascusknow ... m/www/home
and you can access the following directly

Damascus Mythology & Reality
Damascus Quality
Barrel Strength and the 1891 Birmingham Proof House Report
Turn-of-the-Century Shotshells
Barrel Evaluation Recommendations and Non-Destructive Testing
Damascus Anomalies & Defects

2. Post your real name. Our credibility depends on our willingness to expose the real us to criticism and critique. I've done it and you can find a lot more about me here
http://www.picturetrail.com/homePage/gr ... almissions

Or not, and you will be arguing with yourself. But please start another thread to share your thoughts, and I'll leave it up to the administrators if they wish to un-sticky this one.

_________________
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Richard Baxter (1615-1691), Directions Against Covetousness
"Be more careful to use what you have, than to get more."

Kingsley Brown "Shoot more, shop less."


Last edited by Drew Hause on Mon Mar 06, 2017 10:25 am, edited 6 times in total.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Wed Oct 08, 2014 6:51 pm 
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I expect I have read most all for your site several times over. It contains an amazing amount of information gleaned from the Net. I have included links to it in several of my posts. I congratulate you on your dedication to the subject. If I have any reservations about your site, it is that much of the information you quote is either undocumented or contradictory.

My agenda? I suppose I have an obsession with facts. It’s my fault; I can’t help correcting major errors especially if they are dangerous. And as I have already pointed out recommending insufficient minimum dimensions for Damascus barrels can be dangerous.

You are a Medical Doctor who apparently places a high belief in the guidance of God. I am a Chemical Engineer who takes his guidance from facts. My real name is Robert S; I don’t give out any other personnel info on the Net for security reasons.

You have a habit of either changing the subject or changing what you just said (which can get a facts oriented person all upset). After I questioned the picture that you claim contains deep pits you now say “Some of the bore defects are pits, some are machine marks from an unfortunate attempt to length a 16 Ga forcing cone, and what you call dents are small bulges.” Can you point out the dents, bulges, machine marks and pits? Or estimate how deep you think they are? Or explain the new and apparently irrelevant picture of rusty steel?

Thanks for reminding me of Barlows’ Formula. There is a calculator at: http://www.aerocomfittings.com/barlows.html

If you plug in 18,500 PSI (the US Proof Pressure which includes the Safety Factor of 7,000 PSI above the maximum allowed pressure of 11,500 for a 12 Ga), the 54,000 PSI Tensile Strength that you quoted for Damascus Steel in the ‘Stress’ box and 0.75” for the approximate diameter for a 12 Ga near the chamber it calculates a required wall thickness of 0.1285”. That’s significantly more than the 0.105” you claim is safe. Like I said, your recommendations could be unsafe for Damascus steel.

Can you explain your statement: “If the barrel is made of Twist with a 50,000 psi tensile strength, that does NOT mean that it will withstand a 10,000 psi load by a factor of 5.”

I can’t even guess what the 1931 DuPont memo is supposed to accomplish.

Since I have met your requirements, except for my last name, I’ll ask again:

Have you been able to find the measured dimensions for your vintage guns that you demand of others? Can you explain why you claim Damascus barrels rust internally on one site then contradict it on another. Do you have any documentation for your apparently unsafe Damascus wall thickness recommendations?


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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Wed Oct 08, 2014 8:56 pm 
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Bob Somebody
Read this again slowly - "Barlow’s refers to a pipe capped at both ends with a static pressure (a pressure cylinder). Shotgun barrels are not designed to be pressure vessels as one end is open and the pressure rises and falls quickly."

You are needlessly insulting.

The image was a test, and you failed. How could you not possibly see the pits, or realize the second image is the same bulge on the outer surface of the barrel??

You've purposefully mischaracterized my statements. Please show where, on this or any other site, that I claimed "rusting welds, voids and pitting occur in Damascus types of steel" and was not quoting another (confused) source.

You choose not to reveal who you are.
I choose not to participate. Carry on.

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"Be more careful to use what you have, than to get more."

Kingsley Brown "Shoot more, shop less."


Last edited by Drew Hause on Sat Jan 09, 2016 4:41 pm, edited 3 times in total.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Thu Oct 09, 2014 5:00 pm 
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Quote:
You are needlessly insulting.
I consider the questions I asked to be necessary; your claims are misleading and may be dangerous.

Quote:
The image was a test, and you failed. How could you not possibly see the pits, or realize the second image is the same bulge on the outer surface of the barrel??
A test? Laughable! You still won’t explain your statement that you should not to shoot a gun with deep pits while, at the same time, you are saying that you cant tell if they are deep. You also posted claims on another site that deep pits don't exist or don't affect strength.

Quote:
You've purposefully mischaracterized my statements.
I didn’t mischaracterize anything. Your claims are demonstrably incorrect. They don't meet published standards for wall thickness or simple strength calculations.

Quote:
You lack the cojones to reveal who you are, though I have a good idea.
I admit it may be an irrational fear to worry when someone try's to track you down. What are you planning on doing if you find me? You've convinced me that I shouldn't give you anything more than my first name.

Bob


Last edited by Bob S on Fri Oct 10, 2014 10:54 am, edited 1 time in total.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Fri Oct 10, 2014 3:46 am 
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Cancelled


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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Fri Oct 10, 2014 1:24 pm 
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I happen to think Bob S makes valid points.
Mr Hause's info seems contradictory and confusing, and he seems to protest too much to any contrary opinions.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Fri Oct 10, 2014 1:46 pm 
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Claysmoke27: if you (or any other contributor) would please
1. Post and document your real name
2. Avoid arrogant and inflammatory comments like "I hate to burst your bubble"
3. Ask for clarification of ONE issue at a time.
I will do my best to answer your question, or refer you to the document on the DamascusKnowledge website that will do so.

Knowledge about vintage barrel safety is important to those of us who enjoy using vintage doubles. I'm always interested in valid differences of opinion, backed up with historical or practical research like a metallurgical analysis. I will not however respond to anonymous and uninformed sniping.

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"Be more careful to use what you have, than to get more."

Kingsley Brown "Shoot more, shop less."


Last edited by Drew Hause on Sat Jan 09, 2016 4:42 pm, edited 1 time in total.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Fri Oct 10, 2014 4:25 pm 
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Why are real names such an issue for you?

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Mon Oct 20, 2014 2:53 pm 
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Proof Testing is the only acceptable method of determining the safety of a gun according to either national or international standards.

If you want your gun proofed you may want to try:
H. P. WHITE LABORATORY, Email: info@hpwhite.com, Phone: +1 410 838 6550,
Or,
Tom Armbrust, Ballistic Research, 1108 W. May Ave, McHenry, IL 60050-8918, 815.385.0037, E-mail - barbmiller49@yahoo.com http://www.armbrust.acf2.org/. (Tom did the standardized pressure testing for Sherman Bell.)
Or,
The Birmingham Proof House, http://www.gunproof.com/. It is recommended to ship through an English Gunsmith who will inspect your gun for safety before it is tested.

My method, which I expect is similar to most everyone who appreciates shooting classic shotguns: I inspect the gun myself, fire it remotely using a string and shells with the highest shot load and velocity I can find and then switch to low pressure loads from there on (to give both my shoulder and an irreplaceable gun a break).

If you aren’t comfortable inspecting an older gun you may want to find a gunsmith who is. Just don’t expect them to tell you a gun is safe; liability!
________________________________________________

The US Standards can be seen at: http://www.saami.org/specifications_and ... ad/209.pdf
The European minimum example wall thicknesses are here: http://www.cip-bobp.org/sites/default/f ... 4-1_EN.pdf.

Equations aren’t be used to determine wall thicknesses. The US Standard doesn’t mention calculations or give any minimum wall thicknesses. The European Standard mentions: “In paragraph 3 in the Appendix some examples of dimensions are given supposing that the metal of the barrel is submitted to artificial static stress. This does not happen in practice of course, because when a shot is fired the stress is applied dynamically in a very short space of time.”

The European Standards’ minimum wall thicknesses examples are based on an unstated relationship to Yield Strength (the force that can be exerted before a permanent deformation occurs) not Tensile Strength (the force required to cause a rupture). Yield Strength is used as the basis for wall dimensions: you wouldn’t want your barrel stretching after every firing. Yield is often 60-70% of Tensile Strength:

“3.1. Calculation of Wall Thickness"

"The wall thickness given to firearm barrels, so as to guarantee that the gun can be used with complete safety is conditional on the steel utilised. This calculation is complex and carries additionally a subjective element in that there is the question of defining the co-efficients of safety (that is to say, the relationship between maximum stress (me: Force/Area) on the barrel section and the elastic limit (me: aka Yield Strength) of the steel). There exist several Bibliographical references and the long experience of the Proof Houses concerning this question."

"Accordingly, a minimum wall thickness for the barrel and chamber assuming proper concentricity has been fixed for each steel category.”

The gun manufacturer is still responsible for setting the actual wall thickness based on Proof Testing.
_______________________________

Modern SAE/AISI steel specifications are based on Chemical Composition, not Mechanical Properties. A brochure for 4140 steel from a supplier can be seen at: http://www.speedymetals.com/information/Material43.html.

Note that it is the steel Composition is fixed by a specification. The strengths aren’t specified. They can vary over a wide range depending on the Heat Treatments given to it by the end user, e.g., in the brochure Yield Strengths shown are from 65,000 PSI when in the Soft Annealed state up to 235,000 PSI when fully Hardened.

See also: http://en.wikipedia.org/wiki/SAE_steel_grades. There are no Mechanical Specs.

The European Proof Standards are 'end-used' recommendations like other end-user oriented standards such as the ASTM Construction standards. They specify the Mechanical Properties required for a particular application and then list typical steels that can meet those Strengths through Heat Treatment. (See their steel strength Categories which contain many steel grades. Also at: http://www.cip-bobp.org/sites/default/f ... 4-1_EN.pdf.)

They assume the steel used has been heat treated to meet the strength requirements often making the grade of steel used less important than their treatments:

“2.4. Mechanical Properties:
Steels for use in the manufacture of firearms, after having been heat treated, should possess well defined mechanical properties. Elasticity limit (0.2%), tensile strength, yield point, hardness (which is proportional the tensile strength).”
______________________________________________________

A reference has been made to vintage and some modern steel strengths. Unfortunately they don’t appear to be adequately documented for barrel thickness estimations:

-It is unknown if the vintage steel manufactures’ strength claims are for raw steels that may have only been hot forged to form a billet or if they are ‘typical’ for heat treated steel. They are unlikely be for the steel as-used by the gun manufacturer since there are many forming and treating steps before the barrels are finished.
-The strengths for the three modern steels listed refer to ‘published industry standards’ even though modern steel standards don’t specify strengths.
-The strengths taken from the gun manufacturers claims may or may not be for finished and heat treated barrels and the manufacturer can change the steel used or its treatments at will. Gun manufactures don’t have their own steel mills so they rely on steel manufactures for the development of the steels they use. The steel that was used to make a barrel with a name like Marlin’s ‘Special Smokeless Steel’ was likely sold to any user who wanted it.
______________________________________

"The Modern Sportsman's Gun and Rifle: Including Game and Wildfowl, Volume 1, By John Henry Walsh, 1882” http://books.google.com/books?id=OLwUAAAAYAAJ&printsec=frontcover&dq=The+Modern+Sportsman's+Gun+and+Rifle:+Including+Game+and+Wildfowl%22,+Volume+1,+By+John+Henry+Walsh,+1882&hl=en&sa=X&ei=SNpDVJXiEo2syATIjYCgDg&ved=0CB8Q6AEwAA#v=onepage&q=Siemans&f=false
contains a letters from 1882 documenting what was apparently the first time an English shotgun manufacturer switched from Damascus to steel for at least some of its shotgun barrels. (Rifles and muskets had long been made from steel. Go figure.)

The parts I find interesting:

-The gun maker, Webley, didn’t know the Mechanical Properties of the steel they were using for their rifle and shotgun barrels until they asked the supplier, Siemens.
-Webley depended on extended Proof testing from the Birmingham Proof House to ensure the barrels were safe not on measured Mechanical Properties.
-Barrel Wall dimensions were not used. Rather a test barrel was referred to as weighing “1 Lb. 8 Oz. about or about 4 Oz. less than required to make a 7 Lb. gun with ordinary action”. Apparently the weight of a gun was considered at least as important as its wall thickness; it affected both the guns pointing qualities and its' 'felt recoil'.
-The steel had been chosen by the supplier, Siemans, for its ductility making it a lower strength steel. “As a rule, the tensile strength is about 25 to 27 tons per square inch, (55,000- 60,000 PSI) but can increase it if required, with an elongation of 30 per cent, or more in eight inches.”
-It's not clear if any heating was used to form the steel barrels such as hot forging strips around a mandrel to form a tube. Since it was used to replace Damascus in their manufacturing process, this is quite possible. If so, tensile strengths could be quite different.
-They hadn’t given the steel a name yet.
-Siemans states “it is made from specially selected brands of English and foreign irons” indicating that it wasn’t one fixed grade of steel.


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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Thu Oct 23, 2014 4:52 pm 
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Posts: 836
Here is a footnote from "Treatise on the Manufacture of Guns and Text-book of Service Ordnance", England, 1886, referring to differing Mechanical Properties of steel when it is rapidly ruptured compared to being slowly stretched in a hydraulic tester ("statical" or static testing). Specifically they found rapidly stretched steel would elongated more than when slowly stretched. Just the opposite of Silly-Putty!
Image
This is likely the type of phenomena that the CIP refers to when they say: "The wall thickness given to firearm barrels, so as to guarantee that the gun can be used with complete safety is conditional on the steel utilised. This calculation is complex and carries additionally a subjective element in that there is the question of defining the co-efficients of safety (that is to say, the relationship between maximum stress on the barrel section and the elastic limit of the steel)."

The original can be found at: http://books.google.com/books?id=19agAA ... ic&f=false on the bottom of page 6.


Last edited by Bob S on Mon Nov 10, 2014 4:48 pm, edited 1 time in total.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Sun Nov 09, 2014 6:22 pm 
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Location: AZ but dreaming of KS
My then 94 year old Mormon skeet shooting buddy found a 1906 16g 0E Smith in Rexburg, Idaho last summer.

Image

I didn't have my wall thickness gauge at that point, but measured the bore .653 (Hunter Arms standard for that era .650). It did have suspiciously clean bores.
The chambers were 2 9/16" so I got him some 2 1/2" 7/8 oz. loads from William Larkin Moore. He ended up shooting up 4 boxes and the full & fuller chokes broke targets with authority.
Sent it off to Mark Beasland http://www.mbabllc.com for a look over and barrel refinish, and he found the right barrel to be thin and returned the gun with the advice not to shoot it. He noted draw marks and suspected pitting on the exterior of the right barrel had been filed.
My buddy got back to Paradise last weekend and sure 'nuff measured (from the breech) 9" - .032", 12" - .020", 14" - .016", 16" - .018", 20 - .022" on the lateral wall of the right barrel.
Left barrel was fine; .044 at 9" and .028 9" from the muzzle SO it looks like my buddy has a single shot trap gun now. It would be hard to justify $700 for Briley to fit custom full length .410 tubes.

I share the sad story partially because a 108 year old Damascus barrel about HALF of the recommended wall thickness survived 100 7/8 oz. shells without a bulge or rupture. Found a very old report for RST 2 1/2" 7/8 oz. at 1125 fps with 7720 psi by Tom Armbrust.

Psalm 116:6 "The Lord protects the clueless".

_________________
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Richard Baxter (1615-1691), Directions Against Covetousness
"Be more careful to use what you have, than to get more."

Kingsley Brown "Shoot more, shop less."


Last edited by Drew Hause on Mon Jan 11, 2016 4:23 pm, edited 1 time in total.

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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Mon Nov 10, 2014 8:22 pm 
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Popular Mechanics Nov 1915:
The article is from the time that both Pattern Welded (‘Damascus’ types) and plain steel (‘fluid’ steel) shotgun barrels were being made. It states that the names on the barrels are ‘trade names’. That implies that the names did not specify any particular grade of steel or heat treatment. It concludes that all the gun barrels made by reputable manufactures, even the cheaper guns, will be safe to shoot.
Image
See: http://books.google.com/books?id=td8DAA ... &q&f=false


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 Post subject: Re: Is my gun safe to shoot?
PostPosted: Wed Nov 19, 2014 4:43 pm 
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Location: AZ but dreaming of KS
Pressure Summary of shotshells c. 1895-1930s

Black Powder
3 dram / 82 grains 1 1/8 oz. (1200 fps) is about 5000 psi.
1 1/8 oz. 3 Drams Curtis & Harvey’s No. 4, T.S. (82 grains; somewhat similar but not equivalent to medium grain FFg) was about 6500 psi.
1 1/4 oz. 3 1/4 Drams Curtis & Harvey’s No. 4, T.S. was about 8500 psi.

Bulk Smokeless
NOTE: Pressures reported were determined by lead crushers and modern piezoelectric transducer measurements would be about 10% higher.

“1895 Smokeless Powders For Shotguns”
http://books.google.com/books?id=Wv0MAQ ... =PA446&lpg
3 1/4 Dram/40 grains DuPont Bulk Smokeless 1 1/8 oz. = 7440 psi
3 1/4 Dram/44 grains “E.C.” Bulk Smokeless 1 1/8 oz. = 7584 psi

The 1933 edition of ”Smokeless Shotgun Powders” by Wallace Coxe and E.I. du Pont de Nemours & Co. reported the pressure for 3 Dram Eq. with 1 1/4 oz. of DuPont bulk smokeless at 9,600 psi.

Coxe reported 3 1/2 Dram Eq. 1 1/4 oz. loads in 1928:
DuPont Bulk smokeless powder - 11,700 psi
Schultze Bulk smokeless powder - 11,800 psi
28 grains of Ballistite Dense Smokeless - 12,600 psi
40 grains of DuPont Oval Progressive Burning powder - 9,400 psi

Note 28 grains Ballistite is well over the modern SAAMI maximum 2 3/4” and 3” 12g pressure.


In a 1927 Western Cartridge Co. flyer "Super-X The Long Range Load" by Capt. Chas. Askins the 12g duck load is described as 38 1/2 grains DuPont Oval with a breech pressure of 3 3/4 tons or (calculated) 11,480 psi.

The 1963 George Herter “Reloaders Handbook” lists 23 grains (3 1/4 Dr. Eq.) of "Infallible" Dense Smokeless, now Unique, with 1 1/8 oz. shot in a paper case with paper wads (card & fiber) at 8,725 psi. (Courtesy of Mark Ouellette)

More infro
https://docs.google.com/a/damascusknowl ... FU/preview



_________________
http://sites.google.com/a/damascusknowl ... m/www/home

Richard Baxter (1615-1691), Directions Against Covetousness
"Be more careful to use what you have, than to get more."

Kingsley Brown "Shoot more, shop less."


Last edited by Drew Hause on Sun Oct 23, 2016 3:23 pm, edited 4 times in total.

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