Pressure loads

[Drew Hause]

Michael: this is important
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) so does not work well for unobstructed shotgun barrels; which 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
Shotgun barrels are "thin wall cylinders"
σ = pr/t
p= pressure; r is the inside radius; t is the wall thickness

BTW: 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 only 5,600 psi.

[Michael rivers]

I get your point the reason I wanted to know because the way people talk about old guns it is very unnerving and almost put me off buying a good old piece of history.

[todd allen]

Parker's are not just any "old guns". If you want to see something amazing, see if you can track down the Double Gun Journal article by Sherman Bell called "Finding Out For Myself".
Mr. Bell does pressure tests on old Parker Damascus barreled guns. He uses old rattlely worn out guns, just to make it interesting. Runs blue pill proof loads through them, gradually increasing the pressures of the loads, to see how far they would go before they burst.
They went out to 30,000 lbs plus, before showing any signs of stress.
For the record, none burst.

[Stan Hillis]

Michael, the best information, IMO, to figure out what I think you are trying to determine, is the pressure data for commonly sold shells that were in service during the time the guns were made and used. Much data exists on what those pressures were. Many readily available loadings of the day were in the same range as our modern shells (up in the 10,000 psi range).

A comparison using pressures necessary to cause a gun to fail when new would be useless unless you knew what it would take to cause that same gun, after 100 years of use, to fail. Bell comes the closest, in modern times, to doing that of anybody we know of. But, it's only 100% valid for that particular gun, because of the way condition varies so much with vintage guns. It may, however, be somewhat meaningful for us.

Some have graciously posted charts and figures that show the pressures of vintage loadings, and you could probably find them with some searching, or they may read this and repost them.

When we call a loading a "lower pressure" load it is usually the result of a personal comparison of the pressure of the load(s) in question with the pressures of the loads of the day. I base that call on the individual gun in question ....... it's condition, and what it was designed to shoot originally. I've loaded and used shells that range anywhere from 5500 - 10,500 psi in my vintage guns, though not all of them were "lower pressure" loads. Remember, higher pressure does not hurt wood on a gun. It only places increased stresses on the action, the lockup and the the barrels. Recoil resulting from a heavy payload, and higher velocities, is what is a detriment to old wood in poor condition.

So, what it comes down to is whatever an individual considers "low pressure". If the gun was designed to shoot 10,000 psi commercially loaded shells I personally consider anything from 8500 psi down as being "low pressure". Others would not consider 8500 psi "low", but it certainly is lower.

[Dean Romig]

I stand corrected - thank you Edgar. I had a gut feeling you would come on and do that. So thank you for ‘simplifying’ it all for us.
Your background in metals production, forging, etc. and your training and experience in metalurgy qualifies you to do so... so again Thank You. I used the wrong term. You used the right term and backed it up with data.

I guess my response to Mr. Rivers was meant to direct him away from any assumptions he may have been making about 75,000 lbs having anything to do with reasonable (sane) loads we should be using in these old guns.





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[Drew Hause]

Here you go
Barrel Steel Strength & Composition
https://docs.google.com/document/d/1...EK8OtPYVA/edit
A pre-WWI Titanic steel barrel was AISI 1030 with an industrial standard tensile strength (which is NOT bursting pressure) of about 75,000; which was similar to most pre-WWI Belgian sources fluid steel tubes used by U.S. makers

Turn-of-the-Century Shotshells, Powder, Proof & Ballistics
https://docs.google.com/document/d/1...UOZEFU/preview

Scroll down about 1/4 for an explanation of Parker Bros. proof testing

The 1893 Parker Bros Catalogue documented proof testing with Smokeless Powder in house
"Our guns are bored on the latest improved system for shooting Nitros, or Smokeless Powder, and all our guns are tested with some one of the most approved makes, and a tag accompanies each gun, giving the results of such a (pattern) test."

A Parker Service and Proof Load table was published in the 1930s and reproduced in the The Parker Story p. 515.
12g 2 3/4” shell Service Pressure is 10,500 psi. Definitive proof used 7.53 Drams Black Powder and 2 oz. shot with a pressure of 15,900 psi. The pressure was no doubt measured using LUP and modern transducer values would be 10-14% higher, or more than 17,500 psi.

LTC Calvin Goddard reported the same numbers in “Army Ordnance”, 1934. He wrote that Parker followed the SAAMI standards of that period: 13,700 psi proof, 9500 psi service for 2 5/8” chamber; 15,900 psi proof, 10,500 psi service for 2 3/4” chamber (by LUP) + 10-14% for modern transducer measurement.

[Michael rivers]

Originally Posted by Drew Hause

Here you go
Barrel Steel Strength & Composition
https://docs.google.com/document/d/1...EK8OtPYVA/edit
A pre-WWI Titanic steel barrel was AISI 1030 with an industrial standard tensile strength (which is NOT bursting pressure) of about 75,000; which was similar to most pre-WWI Belgian sources fluid steel tubes used by U.S. makers

Turn-of-the-Century Shotshells, Powder, Proof & Ballistics
https://docs.google.com/document/d/1...UOZEFU/preview

Scroll down about 1/4 for an explanation of Parker Bros. proof testing



The 1893 Parker Bros Catalogue documented proof testing with Smokeless Powder in house
"Our guns are bored on the latest improved system for shooting Nitros, or Smokeless Powder, and all our guns are tested with some one of the most approved makes, and a tag accompanies each gun, giving the results of such a (pattern) test."

A Parker Service and Proof Load table was published in the 1930s and reproduced in the The Parker Story p. 515.
12g 2 3/4” shell Service Pressure is 10,500 psi. Definitive proof used 7.53 Drams Black Powder and 2 oz. shot with a pressure of 15,900 psi. The pressure was no doubt measured using LUP and modern transducer values would be 10-14% higher, or more than 17,500 psi.

LTC Calvin Goddard reported the same numbers in “Army Ordnance”, 1934. He wrote that Parker followed the SAAMI standards of that period: 13,700 psi proof, 9500 psi service for 2 5/8” chamber; 15,900 psi proof, 10,500 psi service for 2 3/4” chamber (by LUP) + 10-14% for modern transducer measurement.

Great! Thanks so much for that info. I just need to know facts instead of assumptions.

[Michael rivers]

There’s no argument here all I need to know is what test did Parker’s bro’s do on there barrels
So no ones right or wrong I’m asking for data that Parker bro’s held.

[Jay Oliver]

That is a great resource right there...Thanks for posting that Drew! What a valuable list.

I have been wanting to get some of those articles and back issues and didn't quite know where to start.

Thanks again!

[Cameron Thraen]

I have read each article. The work they completed, with precision and attention to detail, was excellent. If only I had this information in my early days when I either passed on or sold a few really nice Parkers and other Damascus barreled guns on the old gunsmiths advice "wall hanger, shoot it and you'll lose your fingers". I remember, long ago, a particularly stunning Parker D that I could have purchased except for a gunsmith's opinion that he could detect a 'stretching' in the Damascus at the breech end so I passed. Sigh.