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BrentD, Prof, bushveld, campero, Dan S. W., David Williamson, DoubleTake, Drew Hause, eeb, Ghostrider, graybeardtmm3, greener4me, Hammergun, Imperdix, keith, LeFusil, limapapa, mc, Parabola, SKB, Stanton Hillis, TCN, Ted Schefelbein, Woodreaux, WRE1
Total Likes: 75
Original Post (Thread Starter)
#615160 05/26/2022 5:56 PM
by Drew Hause
Drew Hause
Dewey Vicknair's blog

DeFelsko PosiTector UTG P1

Steel measuring range 0.008" to 0.475"

Dewey is free to his opinion, but documentation that the newer ultrasound devices are more accurate than the pin and gauge tools would require comparison of both techniques on multiple barrels.

When Bill Henry made my tool, he also made a standard segment of .038" thickness with which I could 'zero' the gauge, and could (and do) recheck frequently during the measuring process. If my gauge has been set to the .038" 'zero', repeatedly measures the wall thickness at the same number (say .045 at 9"), and when checked is still set at .038" I believe the measurement is accurate. Flexing of the round support bar does not seem to be relevant to the relationship between the pin on the bar and the pin of the gauge, unless I contact the barrel wall with the bar.

[Linked Image from photos.smugmug.com]

The use of Ultrasonic NDT is an entirely different issue. Scroll down about 1/2 way here for a summary and links

I can't comment if the new high resolution US devices can detect defects within the wall of fluid steel or pattern welded barrels.

The problem with RT is in differentiating surface defects (pits) from defects within barrel

[Linked Image from photos.smugmug.com]

A few smiths and NDT labs have examined pattern welded barrels, but there are no industrial standards for the interpretation of those tests.
Both MPI and RT might be helpful to show microscopic through cracks in a pattern welded tube.
Obviously a great deal of research would need to be performed to determine if US can find hidden defects/voids/inclusions in pattern welded tubes, but the industrial money is not in testing a few vintage shotgun barrels.

Bottom line: if you want assurance as to the safety of your barrel, beyond a bore scope exam and expert wall thickness measurements, have them proved at a pressure of 1 1/2 X the pressure of the load you intend to use. And there are testing labs in the U.S. that will do that.
Liked Replies
#616019 Jun 23rd a 02:12 PM
by mc
No doubletake even ultrasonic can't penetrate that.
5 members like this
#620973 Oct 21st a 10:54 AM
by SKB
Most light game guns were made with thin tubes, .025" or less when new. You really need to look at the original bore diameter and barrel wall to understand what you have and how safe it is. I have no issues with a gun that is thin out towards the muzzles as long as it has plenty of wall thickness in the first 9" or so and it's price reflects the barrel condition.
5 members like this
#616705 Jul 14th a 04:53 PM
by LeFusil
Ed Good= The Sanford & Sons of guns.

You suck Ed. Always have. Always will. You attention seeking idiot.😂
4 members like this
#616000 Jun 22nd a 11:54 PM
by LeFusil
My gauge. Accurate. Rigid. Repeatable. IMO, your gauge is only as good as the quality of your indicator.

I have a Manson too, but I hate it. The Manson is ok in pinch, but I really don’t like messing with the damn thing if I don’t have to.

[Linked Image from i.ibb.co]
3 members like this
#615669 Jun 10th a 03:07 PM
by damascus
I did find this interesting reading especially in the way things have changed when I was purchasing guns here in the past. Especially if you did what I did was to purchase guns at local auctions with the best guns always being a farm auctions, these nearly always had the lowest prices though with the largest risk of coming away with a bad purchase. It was always caveat Emptor with no returns. Now a lot of guns where as you could say especially polished up for the event with barrels well reamed and polished for the occasion so you had to be able to spot them easily. My main interest was 12 bore because this was the most popular gauge here because smaller bores the cartridge where more expensive and not popular with the only exception was the .410. Now I am sure you all know that a tenth of an inch on this side of the pond can turn a gun from desireable to junk instantly. So to put the odds in my favour I would have two Gauge's that I built on the kitchen table one was a go no go bore Gauge with two interchangeable inserts .729 inch the standard 12 bore barrel diameter and the other .740 inch the end of the line for a 12 bore barrel having a 9 inch stop. The other Gauge was a short light pocket version of a standard barrel wall thickness gauge that was also set to 9 inches, this 9 inch distance from the breech is where the guns bore is measured also the wall thickness and to be sure measure the barrel thickness 9 inches from the muzzle. So if the .740 inch went into to the bore 9 inches though I have had it go in the bore to the handle the gun was out of proof though all was not lost if the barrel wall thickness was over thirty thousands of an inch there was a good chance of re proof but only if there was enough thickness at 9 inches from the muzzle say twenty five thousands. Though you did have to use your judgment of how much metal would be left after all the pitting if any was removed, so the gun did have to be a top maker in good condition to take a risk. The other rod for the wall thickness gauge was for .410 though hardly ever used the two Tdi's one Metric and the other Imperial. Though now all this is now done for you because last time I went to a sales show there where Gauges on every sellers table

[Linked Image from i.imgur.com]
3 members like this
#616006 Jun 23rd a 02:07 AM
by LeFusil
To comment on Stan’s post…..

Dewey is entitled to his opinion. He’s a very talented, extremely skilled individual, there’s no denying that. His opinions and views carry a lot of weight with people involved in our hobby, especially with individuals who are also interested and participate in the mechanical side of the hobby.
I’m too am entitled to my own opinion, an opinion that has been formed from years of my own personal experience in addition to watching, and LISTENING, to many other, equally talented, sometimes vastly more experienced gunmakers than Dewey, especially ones that have a “speciality like barrel making, stocking, etc.
I take it all into consideration, pick up on the things that make sense to me, ask a lot of questions, do a lot of thinking, contemplating and then form my very own, personalized opinion on the subject.

I emphatically disagree with his assessment on the use of mechanical gauges in regards to measuring wall thicknesses on barrels. In fact, I think it’s total bullshit. I’ve seen some of the very best in the business use mechanical gauges to great effect. And some of the finest guns in the world made today are still being made with the use of mechanical gauges just like the one I pictured earlier. There, that’s my opinion on it.😂.
Does that mean that I also disagree with his opinions on spring making, metal working, bad vs good gun designs, etc. Hell no. I agree with a lot of what Dewey has to say on a myriad of gun related subjects. I still wish he posted here and shared more of his experience and knowledge, but I fully understand why he boosted out of this place too.
3 members like this
#616228 Jun 29th a 05:02 PM
by mc
Well edd that says it all all the great information given to you free and this is how you apply this information ,why in the world did you keep asking for technical information and standards for judging shotgun safety when you have no intention of using it .let the buyer beware is the ultimate resonsability of anyone dealing with you
3 members like this
#621014 Oct 22nd a 05:23 PM
by TCN
Apropos of nothing and offered only as a funny anecdote, not to support a viewpoint . . . I was talking to an old engineer I used to shoot with about what I thought were some very thin barrels that he was shooting with. “Aren’t you worried?” I asked. He said he wasn’t and I persisted “why not?”

“For the same reason that the walls of my cartridges don’t burst, pressure takes the path of least resistance”.
3 members like this
by mc
Edd don't be so hard on your self I'm sure your lost most days when you wake up
2 members like this
by Drew Hause
Drew Hause
I found Bill's protocol from 2012, with additional discussion
1. My gauge has a 5/16" hole in the "block", so I installed an eye bolt in the hole with the eye facing out.
2. I tied a generous loop of clothesline rope to the eye bolt with loops and knots to make holding on easier.
3. You need an assistant if measuring at a gun show or auction. The assistant needs no skill or strength.
4. The assistant will hold the barrels steady on a table with a cushion and the end to be measured over the edge. An assistant is to be preferred over a vise or weights, especially at a show or auction. No weight is heavy enough to hold the barrels steady.
5. The micrometer is zeroed with the rope holding one end horizontally and the ball supported at the other end by the fingers.
6. With the micrometer properly zeroed, the ball end is inserted into the barrel, run from the open end of the barrel to the extent of the rod and the results recorded. The rod must not contact the interior barrel wall for accurate results.
7. The assistant will rotate the barrels on the pad 90 degrees and the results recorded as in the previous instructions.
8. Another 90 degree rotation will complete the measurement of that end of that barrel. The fourth quadrant cannot be measured.
9. Do the same to the other barrel.
10. Reverse the direction of the barrels and do the same from the other end. This should result in 12 recorded minimum thickness measurements from one set of barrels.

I put 25# in the box in which I carry the gauge, and use bungie cords to affix the barrel. I can rotate the barrel while watching the gauge, but do need an assistant to record the results

[Linked Image from photos.smugmug.com]

And thank you dblgnfix for this post, which William apparently missed.
I make my own wall thickness gauge similar to the one Drew has in his post. I have verified its reading via other methods such as cross sectioning ultra sonic and eddy current. They all give the same reading within .0006" which wouldn't make the slightest difference.

And no, this thread is not about you William.
2 members like this
by eightbore
Dr. Drew, thank you for posting my old post about how to use the Manson gauge in a horizontal position, either at a gun show or in your kitchen. If you read carefully, everything you need to know is in my post. Remember, it was taught to me by Jon Hosford, I didn't invent it. I was a machinist in training in my youth, but nowhere near as talented as Jon Hosford. It is about as simple a method for the use of the Manson gauge as you can find anywhere.
2 members like this
#616179 Jun 28th a 02:17 AM
by eeb
You misunderstand my comment. I agree with doing your due diligence and caveat emptor, etc. Whether you’re buying a shotgun or a used car, have it checked out by someone who knows what they’re doing if you don’t have that expertise. British proof laws give the buyer in the UK some assurance that what is being bought at auction, for instance, has an acceptable degree of safety. An industry association might be able to do it here, but I wouldn’t trust any governmental agency to do it; Uncle Sam has trouble delivering the mail.
2 members like this
#616198 Jun 28th a 02:14 PM
by BrentD, Prof
BrentD, Prof
Originally Posted by ed good
all guns that i sell are guaranreed to be in safe shooting condition, with appropriate ammunition...

Can you get any more cowardly, ed?
2 members like this
#616070 Jun 25th a 02:24 PM
by Stanton Hillis
Stanton Hillis
Originally Posted by mc
Edd,the information is out there on the interwebb but you have to do some work if you are unsure about a guns safety don't sell it.if you don't have the ability to evaluate the condition of a gun don't buy or sell.

As I've said before, even recently, working to find out the answers for himself is against Ed's religion, or lack of work ethic, whichever applies. This has been his modus operandi for as long as he has been a participant. He cannot be coached, or even embarrassed, into changing his "style". I actually believe he gets some weird sort of enjoyment from being chastised.
2 members like this
by mc
I checked a icd 28ga.its .105 at the end of the chamber I have another icd 28 but the barrels are much heavier and it is .130 at the end of the chamber
2 members like this
#616590 Jul 11th a 04:25 AM
by Argo44
Ed, I bought a gun from you. Afterwards I had it inspected and found it had been honed considerably and was out of proof. Still safe to shoot but you never mentioned a word about that in your ad. And that gun, you knew, was meant to be used by my daughter-in-law. I'm still ok with the purchase. But you are the last person on this board to be talking about safe guns. Sorry Ed, you're a very smooth talker but you have zero credibility.
2 members like this
#620918 Oct 19th a 07:17 PM
by Hugh Lomas
Hugh Lomas
TCN, I hope your figures are transposed from Muzzle to Breech. --018" from the breech would be dangerously thin and a real risk of injury to the shooter/bystander. I would be skeptical of anything less than .040" in a light game gun and prefer to see.045" at a point 9" from breech.
2 members like this
by Drew Hause
Drew Hause
I'm not beyond whining (begging) in the interest of science gentlemen wink and would very much like more small gauge end-of-chamber MWT numbers

The ONLY 28g barrel that I've measured was a Phil's Parker checked at Mike's cow pasture shoot in 2020. I did not keep the documentation but as I recall, both end-of-chambers measured about .105"

The earliest 28g pressure I've found were published in Frederick Toms, Sporting Guns and Gunpowder, 1897
with 3/4 oz. and + 10-14%
28 gr. Bulk (2 Dram) – 2.81 tons = 8,322 psi
18 gr. Dense (2 1/2 Dr.Eq.) – 3.01 tons = 8,994 psi

DuPont Brandywine Experimental Station data cited by Charles Askins in 1933, with DuPont Bulk Smokeless Powder
28g 2 Dram 5/8 oz. - 4.66 X 2240 = 10,438 psi + 10 - 14%

Since 28g pressures run higher than larger gauges, it would make sense that the end-of-chamber MWT would be slightly greater.

And a glorious Independence Day to each of you and your family
2 members like this
#616566 Jul 10th a 02:32 PM
by Drew Hause
Drew Hause
Woodreaux: back on p.4 I posted an image of my set-up. Having the barrels secured with bungee cords affixed to a weighted box allows me to rotate the barrel while I'm measuring. Typically the thinnest spot is the lateral wall.
On the report I provide I document only the MWT at the points shown, but will note other numbers (or the location of significant pits seen with the bore scope) under "Comments" if needed.
"Chamber" is chamber length and diameter. The breech end of chambers of c. 1900 12g U.S. doubles is usually .809” -.812”, tapering to .795” - .798”, and unfortunately I've measured some chambers that were honed to remove pits also.

[Linked Image from photos.smugmug.com]

ed will note I have my pattern welded barrel MWT recommendations on the form. Obviously those recommendations can be discussed with the gun owner and modified depending on the barrel composition, based on incomplete but IMHO pretty good data ie. we now have composition analysis and tensile strength testing on a significant sample of vintage barrels:
Twist and Crolle Damascus tensile strength is about 55,000 psi
Winchester Standard Ordnance and other "cold rolled" Bessemer/Decarbonized steels and AISI 1020 are similar in strength at about 60,000 psi
c. 1900 Belgian sourced “Fluid Steel” used by all the U.S. makers (Cockerill, Siemens-Martin & Krupp Open Hearth) and AISI 1030 are similar in strength at 75,000 - 85,000 psi
Krupp Fluss Stahl (Homogeneous Fluid Steel) was introduced about 1890 might be a little stronger
AISI 1040 (and modified), Vickers, Cockerill Acier Universel or Acier Special & Bohler “Blitz” are similar in strength at about 100,000 psi
Winchester Nickel Steel, Marlin “Special Smokeless Steel”, Remington Ordnance Steel, Krupp “Nirosta” (1912 patent NIchtROstender STAhl 21% Chromium / 7% Nickel Stainless Steel introduced in 1913), 4140 Chrome Moly (not used until after 1930s) and 4340 (Chromium, Nickel and Molybdenum) are all similar in strength at > 115,000 psi
2 members like this
#620994 Oct 21st a 09:22 PM
by eeb
Originally Posted by TCN
Because you are worried about denting/repairing or because you think there’s a potential for a random burst at that thickness?

My first concern with vintage guns is safety. I’m with SKB on this in regards to location of the thin spot of the barrel. If it’s .025 towards the muzzle, no problem. If it’s .025” at the end of the forend where my hand is, no go. More dealers are disclosing the MBT, but they don’t say where on the barrel the thin spot is. That’s what you ask when you call them up. These tolerances are simply my personal policy, YMMV.
2 members like this
by dblgnfix
I make my own wall thickness gage similar to the one Drew has in his post. I have verified its reading via other methods such as cross sectioning
ultra sonic and eddy current. They all give the same reading within .0006" which wouldn't make the slightest difference.
1 member likes this
by ed good
ed good
blah, blah blah....

it is all meaningless, unless you establish some minimum standards for operator safety...

my standard is .090 in front of the chambers and .030, 7" down from the muzzles...

what are your standards?

sorry, for loosing patience, but you guys dance around this like a bunch of fairies...
1 member likes this
by Entropy
Originally Posted by mc
Edd don't be so hard on your self I'm sure your lost most days when you wake up

Lol. Tough crowd.
1 member likes this
by mc
Keith you are an idiot get back to me when you correct edds "igorant" replys.after hearing your rants for a long time I don't think anyone except edd cares what you have to say you sir Are a turd in the punch bowl
1 member likes this
by Daryl Hallquist
Daryl Hallquist
I have both the vertical gauge and the horizontal gauge. The vertical gauge is inherently not as accurate since one has to deal with the torque generated by the barrel not being measured. Even from a pulley hung in the ceiling the vertical measured barrel is subjected to the torque of the barrel to its side. The often seen brass “rest” on the vertical machines is just “for show” and the seller can manipulate the readings in front of the buyer. The horizontal machine uses only gravity , which is a constant, to generate good readings. I lost a fine gun, sold to a friend , that I thought had thin barrels as measured with my vertical machine. His gunsmith remeasured the wall thickness with a horizontal machine and the barrels were well within the tolerance I would have accepted if I had only known. My vertical machine sits near the furnace, while the horizontal machine is on the workbench.

When using the horizontal machine by myself, I let a half filled bag of shot hold the barrels on the bench. It is easy to turn the barrels, held by the bag of shot, to any position.
1 member likes this
#616010 Jun 23rd a 03:30 AM
by Mark II
Mark II
I didn't know about ultrasonic until lately. So I can't speak to it's accuracy. In a Double gun class I took 3 separate mechanical gauges with 3 people using them came within .001 of each other in measurement so it was repeatable. Does anyone have an idea what an ultrasonic device costs?
1 member likes this
#616069 Jun 25th a 01:44 PM
by mc
Edd,the information is out there on the interwebb but you have to do some work if you are unsure about a guns safety don't sell it.if you don't have the ability to evaluate the condition of a gun don't buy or sell.
1 member likes this
#615707 Jun 12th a 04:16 PM
by Ted Schefelbein
Ted Schefelbein
Originally Posted by ed good
dam, your go, no go gauge idea makes sense, if dealing with uk made guns only...over here we have guns made all over the world, with many different standards...do you have a standard for minimum wall thickness in front of chambers?

ed, why would you persist in the notion (we’ve been over this before) that there exists a magical, minimum, standard bore measurement that would be correct for all guns, old, new, of different gauge, and built in different countries of different qualities of steel?

Why do you persist in hounding people, seeking this magic number? This is not the first time you have attempted to wrangle a simple answer to this complex question. The answer is the same as the last time you asked.


PS UK proof is of use to anyone buying a gun in signature countries of the proof law, most of Europe. Further, it is of use to people here, in the US, for knowing the bore dimensions of a gun, what the service level of use the gun was designed for, and whether those bore dimensions have changed, since the time of proof.
1 member likes this
#616182 Jun 28th a 04:34 AM
by Ghostrider
Ed you replied to my post.”why for do you ax.” I believe you meant to write the word ask.
I ask because you are a licensed Gun dealer and publicly stated your standard of .090/.030. You have not mentioned the equipment or the method used for taking these measurements to assure not only the guns you buy are safe. More importantly whether it is it safe to assume that all the shotguns you sell have bores that meet your personal minimum safety standard?
Many of the members have shared the tools and methods they use. I think it’s a fair question, what do you use?
1 member likes this
#616092 Jun 26th a 02:31 PM
by Drew Hause
Drew Hause
Hermano campero. I have a bit of 'campero' PTSD wink Pollo Campero is sorta the Kentucky Fried Chicken of Guatemala, and on one of our mission trips 2 of the team members went with brother Gideons to the next town and had lunch at Campero. They returned with Norovirus and the whole team got sick! The inside bathroom was continually occupied and folks were running to the outhouse and the family dogs thought it was great fun to chase and watch the Gringos smile

The answer to your question illustrates why the answer is rarely simple.

The best answer is "To what service and proof pressures was the barrel proved?"
1300 kg/cm² is about 18,500 psi
CIP 12g “High performance/Superior Proof” is 1320 BAR = 19,145 psi for a Maximum Average (Service) Pressure 1050 BAR = 15,229 psi
Contrary to the mythology, U.S. makers of vintage doubles DID prove their guns (using pattern welded and fluid steel tubes that had been proved in Belgium) at 16,000 - 18,000 psi

If your gunsmith calculated that pressure based on a bursting or hoop stress formula, which don't work well for unobstructed shotgun barrels, he needed to know the steel tensile strength.
Is the barrel pattern welded or fluid steel? Siemens, Cockerill or Krupp?

1.5 - 2 mm = about .06 - .079"
I assume that is the minimum wall thickness and certainly not the end-of-chamber, which we also need to know (and the 9" from the breech would be helpful also)

The gun is a 12g? What does the bore measure and is there evidence of honing or other barrel modification?

Bell ringing MAY indicate the rib is tight, but little else.
1 member likes this
#616093 Jun 26th a 03:19 PM
by campero
Thanks for your reply!

I call myself a campero because I love the countryside, hunting and nature 😅😅 no chicken 😅😅.

I wrote on this forum about this gun. It is a 28 ga Wiggan & Elliott. It has a 28 ga chamber but a 30" 24 bore barrel: overvored! You can see pictures if you look for.

Don't know what steel, but it rings like a bell.

I test fired my Wiggan and my B525. It was amazing. Faster shooting with the old single barrel than with the new over-and-under, but this is other post (sorry).

[Linked Image from i.ibb.co]

Best regards!
1 member likes this
by ed good
ed good
no one else here or anywhere else for that matter, seems to make a big deal about barrel wall thickness in front of chambers...

come to think of it, of the hundreds of doublegons that i have sold over the years, i do not recall any one asking about the barrel wall thickness in front of the chambers...

maybe my concerns about shooter safety are much to do about nothing?

and now we learn from jack rowe, that only .020 9" down from the muzzles is ok...

so, logic says to stop measuring barrel walls, cause hit dont make no difference no how?
1 member likes this
#616048 Jun 24th a 05:27 PM
by Drew Hause
Drew Hause
If I give you an answer will you stop ed?

Wall thickness recommendations can reliably be made based on the measurement a large sample of unmolested barrels; for my purpose vintage pattern welded and fluid steel. That data has been posted.

Recommendations for vintage shotguns are however dependent on:
The tensile strength of the steel used to fabricate the barrel
The presence of pits as determined by visualization with a bore scope or camera. Mechanical gauges are unable to measure the thickness at the bottom of pits; I would be very interested if the current ultrasonic devices can do so.
The pressure of the load the shooter intends to use

SO examiners must individualize their advice. Simple minds want simple answers ed but it's not that easy.
1 member likes this
#620647 Oct 13th a 08:30 PM
by ed good
ed good
well bore, i like fred...fred is fine by me...

as for you, bore is very appropriate...
1 member likes this
#620669 Oct 14th a 02:08 AM
by mc
How did ed remotely proof the barrels ,does winchester sell proof loads and what gun are the proof loads ment for a field gun? Duck gun 3inch mag gun are are guns created equal .are the winchester proof loads equal to Parker proof loads what criteria was used to analyze the gun for damage or was it. "hey it didn't blow up"
1 member likes this
#620926 Oct 20th a 04:15 AM
by KY Jon
KY Jon
There are no set rules about bore diameters, only that they shall be measured and stamped. That said I have seen 12's with tight bores and what we think of as over bores all being original. As to your left barrel it sounds like some removed a bit of metal to try to get some choke effect in a cylinder gun.
1 member likes this
by Drew Hause
Drew Hause
Hermano Campero: a helpful chart from “Proof Tests and Proof Marks: Practices of Manufacturers in the United States”, 1934. Limits are based on the 1925 British Rules of Proof. Long tons are converted to PSI simply by X 2240, and the numbers were measured by LUP so require adding 10 - 14% for modern piezo transducer numbers.
It is important to note that the standard 28g load then was 5/8 oz. and 2 1/2" .410 only 3/8 oz. The 2" .410 was 3/10 oz.

[Linked Image from photos.smugmug.com]

Modern U.S. SAMMI standards for 28g and 2 1/2" .410 allow max. pressure of 12,500 psi; 3" .410 13,500 psi.
12g and 16g are 11,500 psi and 20g 12,000 psi

The current CIP standards allow for greater pressure https://www.scribd.com/document/97965210/CIP-Shotshell-Pressures
28g is the same as 24g

[Linked Image from photos.smugmug.com]

but slightly LESS end-of-chamber wall thickness for small gauges, but the Category 1 “Standard Steel” is Non-alloy AISI 1045 with tensile strength = 101,526-123,137 psi
Category 2 is Non-alloy AISI 1060 and 3 Alloy with 3% Chromium and 2% Molybdenum with a Tensile Strength of 116,030 - 159,396 psi
1 member likes this
#620938 Oct 20th a 05:25 PM
by mc
It can have meaning when you check the diameter to the proof if the difference is great it could mean thin walls or if a type of gun was traditionally 729 bores and it's now 740 might indicate wall thickness problems.so bore diameter might be important
1 member likes this
#621029 Oct 22nd a 11:45 PM
by Drew Hause
Drew Hause
There are several bursting formula:

Barlow's Formula P = 2 x S x 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 preferred the Alger Burst Formula
Burst pressure = Ultimate tensile strength x 3(OD – ID) / OD + 2xID

Lame Formula
Burst pressure psi = Ultimate Tensile strength x (OD squared – ID squared) / OD squared + ID squared

Mechanical engineers (plural) with whom I have discussed barrel bursts explained that all 3 apply to a pressure vessel; a pipe capped at both ends.
An UNOBSTRUCTED shotgun barrel is very very briefly "obstructed" by the ejecta, which very quickly begins to move in response to the gas pressure, which then rapidly falls.

[Linked Image from photos.smugmug.com]

SO the bursting formula do not work well for non-obstructional shotgun barrel bursts

Anywhere along the length of the tube where the gas pressure exceeds the bursting pressure, the burst becomes the "path of least resistance."
1 member likes this
#621039 Oct 23rd a 10:43 AM
by Stanton Hillis
Stanton Hillis
Originally Posted by Drew Hause
An UNOBSTRUCTED shotgun barrel is very very briefly "obstructed" by the ejecta, which very quickly begins to move in response to the gas pressure, which then rapidly falls.

This is exactly why I have so much problem believing that an overloaded (double charged, wrong powder, etc) shell, will ever burst the barrel wall several inches down bore. The pressure on that curve is down to ~2000 psi at 7 inches from the breech. That's less pressure than my JD tractors' working hydraulic pressures, and they are contained in some very thin walled tubing and run for thousands of hours at those pressures, including pressure spikes.

Until proven wrong with empirical data I will always believe a down bore barrel burst is caused by an obstruction other than the payload itself.
1 member likes this
#621047 Oct 23rd a 12:56 PM
by Drew Hause
Drew Hause
A very helpful pressure-distance graph dated June 10, 1929, from the McCracken Research Library, Buffalo Bill Center of the West (found by Gary Rennles) and used by permission

The digital image is part of the Winchester Repeating Arms Company Collection but includes a notation “Hunter Arms Co”. WRAC was acquired by Western Cartridge Co. Dec. 22, 1931, so it is impossible to know if the curve was generated by Winchester, Western, Hunter Arms, or (very possibly) the Burnside Laboratory of the E.I. du Pont de Nemours & Co.

[Linked Image from photos.smugmug.com]

Loaded with FFFg black powder. Shot presumed to be No. 6.
Pressures were measured by crushers (LUP - Lead Units Pressure) and modern piezoelectric transducer measurements would by 10 – 14% higher
F - 10g 2 7/8” 9.5 Drams with 2.36 oz. shot = 16,000 psi
A - 12g 3” 8.265 Drams with 2.187 oz. shot = 17,250 psi
G - 12g 2 3/4” 7.53 Drams with 2 oz. shot = pressure not recorded
B - 12g 2 3/4” 6.5 Drams with 1.687 oz. shot = 14,200 psi
C - 16g 2 9/16” 6.5 Drams with 1.687 oz. shot = 13,750 psi
It seems likely the ‘B’ 12g and ‘C’ 16g labels were switched
D - 20g 2 3/4” 5.74 Drams with 1.5 oz. shot = 14,625 psi
E - .410 2 1/2” 2.377 Drams with .624 oz. = 15,625 psi

1” peak pressures
H - 12g 3” ‘Record’ 1 3/8 oz. shot presumed 1275 – 1295 fps = 13,250 psi
I - 12g 2 3/4” ‘Field’ 1 1/4 oz. shot presumed 1330 fps = 10,750 psi
The label ‘J’ for 28 gr. Ballistite and ‘K’ for 3 1/2 Drams DuPont Bulk appear to have been switched on the pressure curve graph. Dense Ballistite clearly generated greater pressure than DuPont Bulk.
K - 12g 2 3/4” 1 1/4 oz. 28 gr. Ballistite = 12,900 psi
J - 12g 2 3/4” 1 1/4 oz. 3 1/2 Drams DuPont Bulk = 10,000 psi

[Linked Image from photos.smugmug.com]

The pressure curves essentially meet at 5” at 7000 psi; at 10.1” 2625 psi (DuPont Bulk) to 3000 psi; at 15.5” 2000 psi; at 22.1” 1500 psi

[Linked Image from photos.smugmug.com]

More vintage pressure-distance curves are at the bottom here
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