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Originally Posted By: keith

I'm not so sure of how you could prove this statement either... assuming the "increase pressure" you cite is something radically greater than normal chamber pressures. I don't see how anyone could predict the result when a shell is suddenly unsupported by a large portion of rim cut and chamber wall at the moment of near peak pressure. How can you assure us that the rear portion of the brass remained perfectly flat against the breech face, and that there was no violent flexing of the largely unsupported shell head, which may have flattened the rim and permitted the primer to balloon outward? I also don't see how anyone could accurately reproduce the event to confirm this result.

You can cry, or whine, or complain about my opinion here, but I think we all know where you were coming from with your last paragraph in your post above, and your X-Ray Glasses advertisement.


It's all his silly speculation....

Dr. Drew is looking to blame anything but the 100 plus year old gun.

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Fascinating work Dr. Drew. Thanks a bunch. I'm learning,


Baluch are not Brahui, Brahui are Baluch
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I concur. Dr. Hause have you had any Krupp samples from either American offerings wearing Belgian Krupp steel or from German inland offerings w/ Krupp Stahl? Somewhere I have a hahn drilling that some Russian ladies demilled by chopping out rectangles on the underside of the tubes just forward of the chambers. So just how much a sample might be required?

Cheers,

Raimey
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Thank you Raimey. We've got some published Krupp composition studies (a couple of which you likely found) here about 4/5 way down https://docs.google.com/document/d/1dnRLZgcuHfx7uFOHvHCUGnGFiLiset-DTTEK8OtPYVA/edit

Dennis Potter gave me a Krupp segment for the tensile testing, but he did not know the origin or DOM thereof - 113,000 psi!
I didn't have it composition tested however.

I'll decline to test non-U.S. Krupp tubes, but would certainly like to test a Krupp tube from a U.S. maker's gun.

And while we're on the topic, I've got a segment of Fox “Sterlingworth Fluid Compressed Steel” on the way.
A Sterlingworth brochure in 1911 mentioned “chrome-nickel and vanadium steel” barrels and “Chromox High Pressure Fluid Steel” was introduced in 1912
https://books.google.com/books?id=eGvdCgAAQBAJ&pg=PA137&lpg

I'll do both composition and tensile testing, which should be of interest to the Fox fellas.

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Thanks Hause but me thinks if you chase the composition back on any run of the mill Krupp steel tube that all will have their origins in Liege. So with that said, when comparing apples to apples I really don't think there will be much deviation.

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Raimey
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On these obtains stress values, @ what percent of the strength test/value might we see a failure? I guess better stated, if we know the value for which the steel might falter & we know what the given pressure value for the cartridges, then what does the resulting peak pressure from an obstruction / grease / whatever have to approach in order to start to see a failure?



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Raimey
rse

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Having discussed this with a mechanical and metallurgical engineer there is no good answer.

There are of course several bursting formula including 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.

Burrard used the Alger Burst Formula
Burst pressure = Ultimate tensile strength x 3(OD – ID) / OD + 2xID

All the formula (including American Standard, Alger, Lame & others) refer to a pipe capped at both ends with a static pressure (a pressure cylinder). Barlow's refers to a thick wall pressure vessel (wall thickness greater than 1/10 – 1/20 ID).
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
https://www.engineersedge.com/material_science/hoop-stress.htm
Shotgun barrels are “thin wall cylinders”

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.

A study by the Royal Military College of Science, sponsored by the Birmingham Proof House and the British Association for Shooting and Conservation, showed that an obstruction by 2 fibre wads (total weight of 4 grams) was sufficient to bulge or burst a 12 gauge barrel shooting a 28 gram (slightly less than 1 ounce) load. Peak pressure occurred 22mm (.866”) past the leading edge of the obstruction.

re grease:
Tom Roster
“One test European shotgun manufacturers use to fast-proof barrels if standard proofing methodologies and loads are not available, is to liberally oil the bore and then fire a standard service load in it. The well-oiled bore interior will cause the pressure to rise some 6,000 to 7,000 pounds per square inch (PSI) above the Maximum Average Pressure (MAP) for service loads. And grease inside the bore can cause the pressure levels produced by shotshell service loads to easily double."


OTOH there are many studies documenting how difficult is can be to burst a barrel, including Greener's attempts in 1886
http://books.google.com/books?id=inQCAAAAYAAJ&pg=PA92

and of course The Double Gun & Single Shot Journal“Finding Out For Myself” series by Sherman Bell with technical assistance from Tom Armbrust esp.
Vol 18, Issue 1, Spring 2007 -
Destructive testing on a Damascus barrel with thinned walls; calculated by O.D. - I.D. and not measured.
Destructive testing using various obstructions, including a 20g shell.
Destructive testing using a shell loaded with 3 1/4 Drams by volume or 56 grains of Unique (similar to “Infallible”) with 1 1/4 oz. shot. The chamber burst with the first shot. The 3 1/4 Dram Equivalent load is 24 grains of “Infallible”, and 56 grains estimated pressure was 50,000 psi.


In this regard, a Parker fella friend Mechanical Engineer who lives in Vegas was investigating hydraulic pressure testing using some of the tubes I've accumulated; unfortunately life and marriage have gotten in the way.

I've had no contact with Zircon/Ron Graham (a metallurgical engineer) who had collected about 40 barrels for testing, including the Parker barrels destroyed by Bell, for several years.

I'll bet a military ordnance engineer might have an answer. Don't you have any PhD buddies up in Huntsville who could help? smile

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Originally Posted By: Drew Hause


A study by the Royal Military College of Science, sponsored by the Birmingham Proof House and the British Association for Shooting and Conservation, showed that an obstruction by 2 fibre wads (total weight of 4 grams) was sufficient to bulge or burst a 12 gauge barrel shooting a 28 gram (slightly less than 1 ounce) load. Peak pressure occurred 22mm (.866”) past the leading edge of the obstruction.


Any value for said pressure?

Originally Posted By: Drew Hause

I'll bet a military ordnance engineer might have an answer. Don't you have any PhD buddies up in Huntsville who could help? smile


I do such as the >>Rocket City Rednecks<<. But we always preferred non-destructive testing. @ one point in grad school we didn't submit a proposal for non-destructive testing of prophylactics. Can't recall if it was the Government, Trojan or who???

Cheers,

Raimey
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A weakened chamber plus a questionable reload = we will never know. Thats it.

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Another important factor when testing steel is the Yield or Elastic strength. This is the point at which the Stretched steel does not rebound to its original position or the point of a Bulge. This point cannot be simply taken as a given percentage of the Ultimate Tensile strength as some alloys have a yield of a higher percentage then do others.

As a general rule, Damascus & Low Carbon steels will have a lower yield point in relation to their ultimate than will higher alloy steels. This was how the thought was started that Damascus was better than steel because it would bulge while steel would burst. In reality, it only proved that Damascus had a lower yield strength than did the steel.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra
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