I'll probably dribble out information as available, because I NEED YOUR HELP and you are very likely to think of something that should be done, that I did not.
Received the barrel with the empty shells in the chamber, the fragment, the empty shells that had been used, and 4 reloads.
1. I now know what a loose rib 'clunk' sounds like
2. The empties will be examined for missing components/parts
3. The reloads will be opened and the powder weighed.
4. Taking quality pics is very difficult, and I'll try again in the morning when the sun is not as intense.

First impressions
1. The rust shown on the previous pictures is clearly new
2. The chambers have not been messed with; 2 5/8" with a short forcing cone and only the expected tool marks. Wall measurements to follow but they appear adequate

3. The shell in the left chamber came out easily using a long dowel. I don't think the primer shows increase pressure and looked like the other



BUT extractor indentations were present in the steel case head. I may need pro help to get an adequate image, but look at line toward the bottom



4. The fragment was bent almost 90 degrees by the force



the crolle pattern is visible on the inside of the bore BUT NOT ON THE SHELL CASE as previously thought



Chamber and forcing cone inferiorly, barrel bore superiorly




In the morning I'll start measuring every bit of wall that I can get to, check for evidence of a bulge, and try for some more pics. Stay tuned.
I am meeting with the metallurgist at METL next Monday.

Measure the shot charge and of course identify the powder.

Thanks Drew.

Yes, thank you Drew.

Forgive me if I'm showing my ignorance, but if the shells in use were 2 3/4" Remington Gun Club reloads, I would suggest that the above statement should be filed under "Potential Contributing Factors".

I would suspect incorrect powder

Thanks Drew

Here is the load recipe from the Hodgdon site, which the shooter has been using for about 2 years
http://www.hodgdon.com/basic-manual-inquiry.html

Remington Gun Club hulls
1 oz. shot
Win 209 primers
WAA12SL replacement wads
17.5-gr Clays powder using #32 bushing in MEC 9000G

The recipe has 15.7-gr 7100-LUP, 1125 fps; 17.0-gr 8200-LUP, 1180 fps; 18.4-gr 9500-LUP 1235 fps

I'm surprised Hodgdon still reports LUP rather than piezo-electric transducer pressures, which are likely higher.


An unfired/loaded shell measures 2 5/16”
A fired shell 2 11/16”

Drew, it appears from the photo the primer is cratered from the firing pin. What do you see?

Also, you might measure the diameter of the hull's head--it sure appears to have stretched.

Do your pictures indicate a crystalline structure on the fourth picture at 1:00? If it is, it may be telling you something.

bill

I have seen a steel barrel gun that blew at the chamber with shells loaded on a 9000. Double charge was the admitted cause in that instance. With the auto advance with the 9000 it is easier to loose track and get a bloop with no powder and then a double charge. Just a thought. Mark

Thanks

Image of both primers, and comparing the two visually, the blow-out shell primer is slightly proud of the plane of the bottom of the shell, and the copper component slightly bulged



I will measure the shell head as Joe suggested. In this image the left shell is slightly raised from the chamber.

Drew,

I strongly question the appearance of that primer. It looks like classic cratering to me, and flattening at the edges, a sign of high pressure. I've seen this many times when working up max loads for a rifle.

SRH

What Stan said.

+1 to Stan on the primer

So the load is a grain away from modern proof limits. Not much room for errors.

Stan is dead on. It appears the copper began to flow backwards around the firing pin. Clearly over pressure regardless of the age of the gun.

Pete

I find the pic of the hull from the failed bbl. most interesting. It would appear that the cleaner green area w/the jagged tear was in solid contact w/the chamber wall at the time of failure & the 'less green' or 'frosted' portion was subject to burning powder gases [blow back?]. I would find that consistent w/Joe's observation of an expanded head at the uppermost head's [or 'brass'] edge. The fact that the torn area or 'clean green' outer portion of the hull does not show any signs of escaping powder gases is perplexing.

FWIW, I recently fired a 20 ga. Remington G.C. hull [previously several times reloaded] in a 12 ga. gun. It was NOT intentional. I have retained that fired hull. There are some similarities to the hull's outer appearance. My fired 20ga. Remington C.G. hull clearly has an expanded edge at the top of the head and also exhibits similarities in it's outer hull surface being 'frosted' in appearance and the mouth being split in several areas and clearly 'brittle'. I consider myself both lucky and fortunate that the Remington hull was sufficiently strong & well engineered to have withstood my stupidity; error, if you wanna be polite.

Is the chamber's dimension oversized toward the breech end? Could some earlier pits or corrosion have been removed from excessive honing? Just questions.

I have to ask myself if what we are looking at in this particular instance is not the result of an unsized hull minus the head from a previous round stuck in front of the fired round? That reads awkward at best. Said another way, if the previously fired reloaded round was previously fired in a substantively oversized chamber & not resized, could the metal head been ejected alone and the body of the hull become lodged directly in front of the fired round? Could it have been a loaded 20 w/the head still attached? Again, it is but another coupla questions.

First, thanks for the leg work and passion on this situation. Nothing but good can come from this.

I hesitate to add to what's been said, but agree the fired primer is definitely a clear clue to what's happened.

I'll add another thanks Doc Drew for following up.

I may be seeing it wrong, but I believe the fired primer on the right hand side of the pictures shows possible signs of higher pressure than the left blown side. I think that gun has been eating a steady diet of over pressure loads for some reason or another. If all the right components are there, maybe you'll find a bushing throwing a heavy charge.

If a dimension of the gun is causing the pressure signs, you may find similar in the other barrel. I'd still guess that barrel integrity could be questioned , and you may find signs of a bulge. I don't think the red rust has anything to do with this mishap, but I think there're signs of black oxidation or defects that might be preexisting from before the barrel let go.

If they're willing to chat about it, maybe ask the metallurgist why the grain of the steel on these failures seems to be very coarse. Please also pass along thanks to the shooter/owner. Interested to read what you come up with when those reloads come apart. Take care.

Joe Wood and Stan are both correct about the suspicious appearance of the primers. I don't really know how the thickness and hardness of shotshell primer cups compare to rifle primers, so I don't know if valid comparisons can be made. But the sharp edge and seeming extrusion of primer cup material around the firing pin on the blown shell tell me this load, whatever it was, probably exceeded safe limits. I'd sure at least try to get my hands on all of the shells that were used from that particular box that day to measure and check for missing base wads, etc. I know that will depend on whether the shooter picked up all his empties, and what was done with them in the excitement of the aftermath. Thanks for continuing to share. You may never find the true cause, but it's important to at least try.

IMO from reloading rifles for a long long time, the shell on the right side of the most recent photo is the one with the highest pressure. That primer was forced back into the breechface and flattened by that breechface. Saw it on rifles all the time. Difference with a rifle brass is you could also measure the sides of the cartridge case as additional evidence of high pressure as well. IMO the overload took the path of least resistance and it appears the metal of the barrel/breech/chamber gave way before the excessive pressure would have pushed the shell back against the left side breechface. Short version of the above is IMO there may have been quite a few over pressure loads involved.

Just the comparison. Here is a picture of primers.
From the left, 10ga RST factory, Rem. Gun Club Factory, Rem. Gun Club with AA209 reload 5800psi.
I personally don't see much difference to the shells in question. Doesn't the upset around the firing pin have more to do with the length and shape of the firing pin? I believe the extrusion you see around the brass cup is a reflection in both photos. Craig

Thanks Craig, and by comparison the subject primer is clearly backed out of the primer pocket slightly. Is the primer cup made of brass or copper?

Youz guys R killin' me but I do appreciate the (contradictory) help. I'll get to measuring this morning, and will work on more ultra close up images of the shell heads, and the indentation made by the extractor which is quite obvious.

I get that recipe, if we use the "ballpark" formula of LUP + 1,000 = psi, as being pretty close to the modern CIP standard service pressure (NOT proof pressure) maximum of 10,730 psi. Higher pressure than I'd want to go in a vintage gun. I've seen the same blown steel barrel as Mark II, and would definitely wonder about a possible double charge.

Drew, thanks for the latest update.
The Mec #32 bushing would be the right one for 17.5 grs of Clays, mine throws on average 17.6 grs. on my 8567 Grabber and 17.4 on a 600 Jr Mark V.

Looking at all the loads available with using a Remington hull, 1 oz. shot, Clays powder, Win. 209 primer and just substituting a different wad, he could have been in a much lower pressure and not in LUP, which is not very informative now.

In my opinion, clays is not a large flake powder and I still do not believe it bridged and threw a double load. If that was the case, one shell out of that box would have had no powder and would have left the wad in the bore.



I am just glad that he wasn't seriously hurt.

Thanks David. I'll take a pic of the powder also.

Several have alluded to the "chrystalline" appearance of the edges of the burst metal. It is my understanding that burst metal, whether damascus or steel, usually has this same appearance. It is the result of the type of failure, a bursting rather than a tearing and not indicating a prior defect in the metal.

Thanks for the suggestion Joe. I measured the steel case heads, just above the rim:
Loaded shell .806"
Empty (from right chamber) .809
Blown shell (from left chamber) .821

I have about an hour of barrel de-resting and scrubbing before I can even start measuring, but this strange wet stuff is falling from the desert sky, so nothing else much to do

I am sure more than a few people have not or do not pick up on the lup not psi data in the Hodgdon Data Center. Worse some may not understand the difference and "assume" which is always very dangerous. I agree that lup data should be separate or have a footnote attached to it to bring its' difference to easy visual recognition.

It is this reason and my natural paranoid nature that cause me to try to verify reloading information by two different sources.

NOW I remember why I hated Chemistry Lab on Thursday afternoon at MU in an old building looking out at the Columns on Francis Quadrangle where coeds were sunbathing and my Frat brothers were starting the weekend early

THAT was an ordeal. Harvesting the shot was pretty easy. The powder however needed to be gently brushed off the bottom of the wad, and out of the shell case. It's very likely a few flakes are still floating around my office.

Shot: .95, .95, .95, and .90 oz.
Powder: 17.4, 17.6, 17.6, and 17.8 grains and what David posted

Barrel scrubbing next.

BTW: was it black powder that the army fed the soldiers to make them impotent? Hopefully inhaling Clays won't do the same thing

Drew, I would ask the shooter if he ever checks the weight of the powder charge or does he just depend on the bushing chart. If he has not been checking weight of the thrown charge periodically you might have him run his reloader and collect a few samples. I know that I can influence the charge weight thrown on my reloaders by how I handle the equipment. I typically go down a bushing size to prevent heavier than desired charges on the single stage reloaders.

Drew thanks. Mec bars are known to throw light shot drops and depending on the size and antimony that would be about right and would only take a few pellets to make 1 oz.

The powder is .4 grs apart and if the LUP conversion is close to PSI that would be close to SAMMI.

The hull diameter of .821 behind the rim is greatly enlarged, and unless the chamber opening was that large the only way it could get that size is if the gun opened when fired.

Wasn't it Bromide?.In the tea, in England I believe.
That seems like a high psi load for an old Damascus gun,dontcha think?
Perhaps there was an 18+ grainer in the mix with the 17.4,17.6 & 17.8 's...those loads are pushing 10,000 ish,aren't they?.. though hard to tell with LUP
I don't load LUP recipes.They seem hot, never mind with a double tap of powder
franc

Saltpeter Franc - potassium nitrate
http://www.snopes.com/military/saltpeter.asp

Drew, I had to look see.... Bromide
franc

Thanks Franc.


Lots of news, but I still need to measure wall thickness of everything I can get to at the rupture.

The first spot where I can measure the bore is at 3 1/4" and is .750, then 3 1/2" .737, and 3 3/4" .733 where it remains uniformly until the choke constriction starts at 3" from the muzzle. Clearly the barrel expanded as it ruptured, but not like this



The first place I could use the wall thickness gauge was at 4" and it was .112, about the same as the end of the right chamber. At 5" .096 and 9" .060.
9" from the muzzle .039 and MWT was .037 at 5".

After serious cleaning, all the rust came off easily and the bore is without significant pitting.

Will get more pics up, and STILL trying to get a better pic of the extractor indentation on the steel head.

Bottom line: I think the barrel is still at factory specs and we can't blame thin anything, but again will report the wall measurements around the rupture tomorrow.

Drew, great detective work. All of your readings look good. We know the chambers of an L.C. Smith, but it would be nice to know the taper dimensions of this gun with 27/8" chambers.

If I'm not mistaken, potassium nitrate is also used for Nitre Bluing and stump removal (quick acting rotting agent)

David: the chambers are 2 5/8" as expected, with a short forcing cone

Amazing how much better pics turn out with a bright but slightly overcast day







This sure looks like a bulge? I still need to check all the empties for missing parts

Excellent photos, Drew!

With kind regards,
Jani

I was reading Drew's initial work and thought about the 737 Aloha Airlines plane that landed with the front third of the top of the fuselage ripped open---was traced to corrosion and the fact that each time the plane takes off and lands the fuselage is stretched open and closed. This slight movement over time "work hardens" the metal and makes it brittle. I would guess that a shotgun is the same way--each time it is fired the barrel gets a hoop stress as the metal tries to expand. That might be significant in an old barrel

Drew, this was mentioned on the first thread but didn't see any comment from you. Does the plastic hull show the imprint of the damascus twist on it?

I think your 'bulge' observation is correct Drew.

This would appear to not be an over pressure caused chamber explosion at all.

My vote would be something stuck in the forcing cone.

Joe: the crolle pattern was not imprinted onto the hull

And BTW: in the name of science I tried some Birchwood Casey Stock Sheen & Conditioner on the barrels and it clearly cleaned off oxidation and years of crud, added lustre, and enhanced the pattern contrast. I was impressed and wish I had a 'before' pic for comparison

oh boy...oh boy...oh boy...more barrels to play with just arrived! This is better than Christmas

Re the comments concerning "approaching SAAMI" limits:

The shooter was using a recipe of 17.5 grains Clays. His loads were relatively consistent, a couple a little under, one a little over, one 0.3 grains over at 17.8. If we extrapolate from the Hodgdon data, which tells us that a 17 grain powder charge is 8200 LUP and an 18.4 grain powder charge 9500 LUP, then it looks like for each additional 0.1 grain of powder, the pressure increases by about 100 LUP. So, at the heaviest powder charge measured (17.8 grains), that would be about 9000 LUP. Add 1,000 to get psi: 10,000 psi. Yes, I'd say hot for a gun of that vintage . . . but still well under the SAAMI service pressure limit of 11,500 psi. And even under the CIP service pressure ceiling of 10,730 psi for a "standard proof" gun. I'd add that I've seen 9500 psi listed as the service pressure for old American 2 5/8" 12ga loads--but that was from pre-WWII sources, so it would actually be 9500 LUP, or about 10,500 psi. So the load should have been safe . . . but not by the safety margin most of us would like to see in vintage guns.

Glad to see other old-time vets chiming in with saltpeter as the supposed additive to Army chow to keep our raging testosterone under control.

Drew, sorry about the 2 7/8", I did mean to write 2 5/8".

It sure looks like a bilge to me, has from the beginning. Realize also an obstruction this close the the chamber is going to react a bit different than one down at mid barrel. Velocity of the charge is not very high yet so the "Check" is not near so great. While pressure would likely still be greatest at the point of the obstruction, it is also likely that pressure would have increased in the entire chamber up until relieved by the burst. I think you need to try & figure out just what was in that barrel & Why & How it got there. I do not believe that either the gun, nor the load being used, was responsible for this burst.

I agree with Miller. I do not believe it was a double charge, but some obstruction.

I might be misunderstanding you but, whatever caused it was an overpressure issue, whether an obstruction, an overcharge, whatever. From the photo I see that left primer shows signs of high pressure. High pressure is the direct result of an obstruction. If, however, it was an obstruction, IMO it had to be directly in front of the chamber. The "common scenario" I can come up with for that is a base wad being "sucked out" of the case an lodging there. And with the Gun Club hull, it can't be a loose base wad as they are of unibody construction.

One possible scenario would be this: Powder bridged causing a double drop, the shell with no powder just ahead of it on the press was used in the left barrel just prior to the blowout leaving it's wad in the forcing cone, by sheer "luck" the next shell loaded in that left chamber was the double charged one. Combination of an overcharge and a forcing cone obstruction equaled what we see. One would think that if this had occurred the shooter would have noticed the blooper and checked the barrel, however. This is all conjecture, of course, but within the realm of possibility. I know where there is a Boswell that blew almost exactly like this, and it was caused by too hot of a reload.

SRH

Stan: By 'over pressure' I mean a shell loaded 'over pressure', i.e. a loading error.

Since the barrel isn't blown where the pressure is normally the highest, rather the 'bulge' shows just downstream of the forcing cone, no 'double charge' would be necessary to achieve the observed results.

But, as you apparently agree, the direct forensic evidence of a double charge is gone. We can only speculate on that, but we can see the bulge.

I posted this question about a double drop of powder on Shotgun World in the Reloading Forum and this is the responses I received so far and I'm sure there will be more.

http://www.shotgunworld.com/bbs/viewtopic.php?f=13&t=392816&p=3123334#p3123334

I wonder if the slightly backed out primer indicates anything. Maybe pressure, over or not, rose quickly enough for the hull to hold on to the chamber wall without setting back against the face of the action. Maybe, since the primer doesn't appear near as distorted as the case head sounds, the pressure may have been falling when the headspace changed enough to let the primer back out.

I wonder if the shooter ever noticed proud primers on empties before. Does the other barrel show signs that some dimension change might be going on ahead of the chamber. Concentric rings showing, I wonder what might have been cleaned up that few inches into the barrel. Just interesting is all, thanks again Doc Drew.

Thank you David. I'll watch that thread.

Craig: I'll be checking the other empties today.

Off to volunteer at Under One Woof, a satellite Maricopa Co. Animal Control adoption shelter, then will start measuring all the edges.
MCAC is the second busiest animal control in the country; LA Co. is first. The kill rate is about 40% and some days 150 animals go through intake. When the economy crashed, 'migrant' families left in the middle of the night leaving their dogs INSIDE apts. and rental houses, or just turned them out. Some neighborhoods are running with Chihuahuas and Pit mixes (which BTW are the sweetest dogs in the shelter).
Just yesterday a guy was arrested for neglect of his horses
http://www.abc15.com/dpp/news/region_cen...aguila-property
Sherriff Joe has a very active and aggressive animal abuse unit and rehab facility. Dog and cock fighting remains a terrible problem out here.
http://www.mcso.org/Mash/AnimalCruelty.aspx
Sorry for the OT rant but child and animal abuse REALLY gets me going. Some live-in on meth beats his girlfriend's child to death at least once a month out here.

Anyway - talked again to the shooter, and his recollection is that all the previous rounds, and specifically the previous high 7 incomer shot with the left barrel, felt and sounded normal. He thinks the gun remained locked up after the blow out but will check with his squad mates as to who first picked up the gun.

This is Drew's first picture



I doubt there is a bulge in those barrels.

I interpret what I see as the tear started back by the powder charge and peeled forward toward the muzzle. The expansion evident toward the muzzled end of the tear is from the metal being bent back as the piece went forward. In Drew's picture that I posted above I do not see a bulge on the bottom of the barrel compared to the watertable.

The imprint of the extractor on the steel base, the lack of a bulge (in my opinion), and the primer sitting high indicate overpressure.

I have had some erratic results from my 9000 when some trash got caught up in the drop tube. The trash was most likely in an empty cartridge fired on a hunt and then dropped into my gamebag with the dead bird, the muddy dog boot that came off, and the miscellaneous twigs and leaves that fell in as I pushed through the brush.

Hard to assess what happened looking at small two dimensional images. The originals are 2MB and I'd be happy to send anyone the image if you would e-mail be at revdoc2@cox.net

This image looks a lot more like a bulge, starting at the lighter colored 1/2" forcing cone. Most of the lower barrel was blown away so we can't know if the bulge was annular

I know what Mike is looking at and tend to agree. However, both are probably right since the metal would have bulged before reaching its elastic limits and then bursting.

Trash in a hull: any hull that has been in a game vest or on the ground gets a thorough vacumning and inspection before reloading--always! Even clean, once fired hulls get a cursory examination at a minimum. I do not reload with any distractions--no tv and no people in the room. When there is any jam on my 9000 I remove all hulls, reset the charge bar, and begin fresh.

+1

Looking at the deformation of the solder line of top rib in this photo it sure looks like a bulge starting just ahead of the rib extension.

Bulge or distortion from bending, hinging outward, possibly the failure started at the breech end where there seems to have been less ductility. I wonder if the failure started ahead of the chamber why the breech doesn't seem to have peeled back a bit as it tried to hang on.

I tried loading a double charge of my standard skeet round on my MEC 9000 and it proved impossible. Here's the data:

Federal Game hull
17.5 grains Clays (35 grains in this example)
Downrange Federal SO clone
7/8 oz shot

Though the wad ram showed about 50 lbs pressure the wad did not collapse. You can see the wad and shot come up to the lip of the hull. Pre crimping was impossible. Had it been an ounce shot would have spilled everywhere.

Why would an obstruction cause an over pressure in the breech down in the steel hull base? The case seems pretty strong that we had an over pressure because the primer was raised and the extractor was imprinted on the steel base.

We're thinking that's an effect of the obstruction Mike, (as is the bulge) and not a result of a high pressure condition initially in the chamber.

Certainly the result is a huge pressure spike, and that's pushing everywhere until the rupture and big vent off.

Just the primer raised up by itself may not mean an over pressure situation caused it. Usually, snapping of a primer on an empty case or hull will raise the primer. It seems though that some condition allowed the primer to partially lift without being subject to the full pressure of the load, otherwise I'd think the primer might have flowed more or maybe perforated like they do now and then.

Been measuring my digits to numbins' and here goes.

1. I examined 19 empties + right chamber empty
No missing pieces inside nor out
The primer of the blow-out shell is similar to the others
NONE of the empties showed the extractor imprint found on the blow out shell



2. The entrance to both chambers measured .818". Hunter Arms specs is .809" so it's possible the chambers could have been hones slightly?

3. The piece wall thickness



The section which is the forcing cone (superiorly) was .123"
3/16" past the end of the forcing cone was .105"
The MWT was .094"

4. Around the edges of the blow out



5/8" from the breech at the apex of the blow out .150"
At the bottom 1 1/8" from the breech .130"
Moving along the bottom and the front was uniformly .121" to .123"
At the top, 2 5/8" from the breech .119"
The thinnest section was at what I believe to represent the apex of the bulge from 2 1/2-2 1/4" from the breech and was .110"
1 1/4" from the breech .122"
1 1/8" from the breech .126"

My assessment is that even with the likely elastic deformation with the bulge, all wall thicknesses are adequate.

Drew, great work. I agree with your analysis of the wall thickness readings.

Let me add another possible cause of over pressure and a bulge at the point seen. A hang fire can cause something similar. I once had a click-bang hang fire while shooting skeet with a 28 gauge gun, or more accurately, Briley 28 gauge tubes in a 12 gauge Beretta 682. I had reloaded some hulls from a shoot where I had been caught in the rain, and I theorize that one shell still had a drop of water in it that delayed the ignition of the powder until it was at the front of the chamber, where it fully ignited. The result was a ring in the subgauge tube just forward of its joint with the stainless steel chamber. I continued to shoot until the match was finished with the bulged tube with no ill effects. There could be numerous causes for such a delayed ignition, other than a drop of water, but the result is the same, a localized pressure excursion that might be sufficient to cause the damage seen in this case.

I loaded a double load of 7625 48 grs ! In a federal paper hull using my posness warren. I still don't know how i didi it, but i do remember the recoil. No damade to the gun , but it was hard to open and the primer was real flat

IN SUMMARY I'll start with a copy of the usual response from the ShotgunWorld Reloading Forum:

"A Damascus barrel is NOT as strong as steel barrel of the same thickness. Think about how a Damascus barrel is made, there are seams and voids all over it. If you don't believe me have a damascus barrel magnafluxed or x-rayed."

That was not the finding of the 1891 Birmingham Proof House Trial
Please review, and note that Whitworth, Siemens-Martin, and English “Superior Barrel Steel” were tested

http://docs.google.com/document/d/1dnRLZgcuHfx7uFOHvHCUGnGFiLiset-DTTEK8OtPYVA/edit
http://docs.google.com/a/damascusknowled...2Hx4/edit?pli=1

MagnaFlux or PD testing shows defect on the surface, not what is happening within metal.

The primary motivation in analyzing this barrel blow up is to apply modern testing, possibly including SEM, fully recognizing that one more than 100 year old barrel does not represent a statistically significant sample.
I will be meeting Monday with a Metallurgist at METL http://metl.com/services/ to explore analysis options, and if anyone here is interest in something other than BS, they might keep an eye on the DoubleGun thread...or not if more comfortable with mythology
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=356377&page=1

I do appreciate the statements made here regarding the near impossibility of loading a double charge of powder without evidence thereof with visual inspection of the shell/crimp.



What can we say with certainty:
1. The wall thickness of the chamber and barrel wall are adequate

What can we say with confidence, but still only as an (educated) opinion:
1. A powder overload was unlikely
2. The fracture/blow out did not occur along ribband weld lines
3. There is evidence of a bulge, and a bulge means an obstruction

As Mike shared (and thanks again)
Major Sir Gerald Burrard, The Modern Shotgun, Volume III, p. 415:
"In the case of an obstructional burst the really essential evidence is the ring bulge. If there is a ring bulge, there must have been an obstruction; and the absence of a ring bulge is conclusive proof that there could not have been an obstruction."

4. The extractor indentation upon, and expansion of the steel shell head, can be explained by the pressure increase prior to barrel rupture

Anything else?

And the prize goes to James Flynn who made the correct diagnosis back on Jan 27

Monday I will be discussing:
1. composition analysis to see if we can determine a modern equivalent to the iron and steel used in fabricating the barrel
2. the best procedure to evaluate the barrel wall for 'seams and voids', inclusions, and micro-fractures.
3. If there would be any value in PD testing.
4. AND THE MOST IMPORTANT QUESTION - how may we best evaluate the integrity of our pattern welded barrels using non-destructive testing????

Here is a Remington Gun Club loaded with the exact data of the blown gun:

17.5 gr Clays DOUBLED to 35 grains
Downrange clone of Winchester WAA12L wad
1 ounce shot

Wad pressure on my MEC 9000 ran up to about 40 lbs
The hull would not hold the entire shot charge--about 1/16 oz ran over

Something I've never seen discussed at length is, notwithstanding adequate wall thickness etc., can metal fatigue be an overlooked factor in old doubles? Metal fatigue is usually not detectable to the naked eye or through caliper measurements. Yet military research (albeit that research has been mostly done on very, very big guns) has clearly established that metal fatigue in such guns is real and that the safe and useful life of a gun has its limits, even if that gun was always operated within its design specs. Formulas have been developed to predict when a military gun needs to be taken out of service.

Thank you Joe!

Will ask if metal fatigue starts with visible (microscopic) changes.

If you have the hulls previously fired before the event
Do they all have intact base wads?
Mike

All the hulls are one piece, and intact; no missing plastic inside or out.

As this was brought up before, all Remington hulls are one-piece plastic.

Joe, beat me to it, I was going to do the same, thanks.

Bro David: quit messing around with reloads and get those pics of your 0 grade to me; right, top, left and the "Smith Farm Implement" article is done!

Drew, I will. I talked to Jim and he said you were doing this one, so I will get them to you very soon.

Thanks again for the great work that FINALLY had to come out. I know the outcome will be beneficial to all.

I just read ninepointer's post and makes for another interesting story and hopefully does not apply to small bore guns for those of us that like to shoot these old guns.

Drew: Is there ANY chance at all that this was a 20/12 accident?

Not according to the shooter, and you were the 2nd place winner of earliest correct diagnosis

Only a quick question, and not making a judgement. What are the characteristics of a ring bulge. Is there any thought as to why the interior of the barrel that's opposite the blow out does not seem to be pressure affected (on appearance).

The orange peel look of the plastic type deformation of the affected area seems clear. Even if not deformed to the same extent, I'd guess the normal appearing part of the barrel was subject to the same pressure that started bulge prior to it letting go.

There's also a good sized looking pit in the deformed area and signs that some machining may have been done for maybe typical reasons that cleaning up may be done. I'm only curious, and would agree that an obstruction might easily have happened.

Craig: It is hard to tell from small images, but the 'pit' is a crack, and the 'machine marks' are the crolle pattern

I kept saying that you cannot get a double charge of any usual shotgun powder into a hull with a full load of shot, thank you Joe for vindicating me!
Mike

I have been told, by one who did fire a double-load in an AYA, and did replicate the load, that yes, you can put double load of powder in a shell and crimp it, but only in a loader that uses a full length die to support the shell when you crimp it. As with a PW. With a MEC loader, without a supporting die, shot is running out all over so the problem is more obvious.

It would be nice to have a final station that weighed the loaded shell and would warn of an over/under load. With todays electronic scales it really shouldn't be that hard.

What about the double load that Stallones described that happened to him on page 7 of this thread?

SRH

Posted on another forum

"There are reports about NDT and magnaflux inspection of damascus, they are published in any number of reference books."

Gentlemen: I've done a lot of internet searching, but am unsure as to where to look. Does anyone here know of published images of any evaluation of pattern welded barrels?
Thank you!

I imagine you have done as much Damascus research as anyone. I've read a lot and never encountered any published references. That's why I questioned earlier if any of the European Proof Houses might have done and published testing to predict what barrels were most likely to fail proof. Maybe you could press the person who posted that on another forum to elaborate. I'll bet you won't get an answer. To me, the real experts are the ones who can say, "I don't know, but I'll try to find out."

In fact, I've only seen a couple articles on destructive testing which were very limited in scope... the Sherman Bell articles, and the articles by Missouri gunsmith Buck Hamlin who progressively loaded a Lefever with lengthened chambers and pitted barrels until it let loose with "nuclear loads".

I believe we are correct Keith, and have spent a long time trying to find something other than the same collection of BS, mythology and advice on various forums, many of which I have either contributed to, or which have information and images lifted from my website. And the internet has nothing from 'any number of reference books'.

Damascus SWORDS and ARMOUR have been Magnafluxed, but I have not yet found published evidence that a pattern welded shotgun barrel has been examined, despite all the advice out there to do so.

I had a long conversation with a NW gunsmith who HAS extensively tested Damascus barrels by MPI, and he has promised me some images. What we need though is to have a barrel with an abnormality by MPI, then try to blow it up and see if the failure is at that spot; which he has not been given permission to do by the owners of said barrels.

The only actual evaluation that I have found is this, from 'Zircon' back in 2007
http://www.familyfriendsfirearms.com/forum/archive/index.php/t-55364.html

I am doing a failure analysis of a pair of Parker barrels - one set damascus, and the other set homogenous Vulcan “fluid steel”. These barrels were used in the study by Sherman Bell and Tom Armbrust, published in Double Gun Journal. They subjected each barrel to increasingly heavier loads and they both failed at about 30,000 psi. Modern ammo gets up perhaps to 12,000 psi. Most folks that shoot these old gals use shells loaded to the 7,500 psi range.
During the failure analysis I noticed that the fracture length for the Vulcan barrels was substantially longer than for the damascus barrels. A close examination of the fracture surface showed progressive, low cycle fatigue marks on the damascus barrel. The crack advanced slightly with each increasingly higher pressured load. On the Vulcan barrels, both sides failed by a brittle fracture mechanism. By this, I mean the barrels let go in one fell swoop. Even though both sets of barrels failed at 30,000 psi, the behavior of the damascus barrels was superior to the Vulcan barrels, owing to the fact that the Vulcan barrels failed in a brittle fracture mode. A ductile fracture trumps a brittle fracture every time.
One of the (myths) with damascus is that it will fail at the welds where the original rods were forge-welded together. When I looked at this particular set of damascus barrels using a metallographically prepared sample, and up to 1,000X optical magnification, I saw NO EVIDENCE of weld joint failure, slag in the weld joints, porosity in the weld joints, etc. I have about 30 old barrels in this study, homogenous, damascus, and twist included. I am a practicing metallurgist who holds an M.S. degree, and am qualified to state the observations of barrel integrity made in this posting.
On the two old Parker barrels, there is a screw hole that comes up from the bottom and pins the extractors in place. Both barrels failed at that hole, because it takes a (segment) out of the side of the chamber and is the thinnest portion of the chambered area.
The damascus barrel let go by a mechanism known as low cycle fatigue. Each succeeding round had higher and higher pressure. After several rounds, a crack started at the extractor screw hole. Each successive round caused the crack to open up just a bit further, until finally the overpressure could not be contained and the (barrel) failed in a ductile fashion. Ductile failures in steel look like a taffy pull at about 1500 to 3000X magnification using scanning electron microscopy. There is a cup and cone appearance with a lot of micro-voids present. This appearance is a dead-set giveaway to a ductile fracture.
The "fluid steel" barrel failed by brittle rupture. The fracture surface is more or less smooth, but has some "rivulets" in it that point back towards the initiation point, which again was the screw hole. The fracture surface was about 3X as long as for the damascus barrels. In other words, the same 30,000 psi final internal load created a lot more fracture surface in the homogenous barrel than in the damascus barrel. This indicates that, for an equivalent-length fracture, it took less energy to open up the homogeneous barrel than for the damascus barrel. The words in the Sherman Bell article were that the Vulcan barrel failed much more abruptly and (violently) than the damascus barrel.
So the verbal description of the failures during firing and the visual observations of the fracture surfaces are in accord with each other. Both barrels ripped lengthwise for some distance and then the rupture terminated in a circumferential crack. In the case of the damascus barrels the crack spiraled around with the weld pattern, but it was not on a weld, rather it was on one of the in-between areas. After the damascus pattern is formed by wrapping rods together and forging them into a strip (the "skelp") which is wrapped around a mandrel, spiral paper-tube fashion, and is forge welded together. These spiral welds remained tight and the parent metal is what failed. This may seem pretty amazing, but in many, many instances the actual steel welded structure is stronger than parent metal.
Many microphotographs, chemical analysis of the steel, etc. (will) make up the (anticipated) article. I'll also be looking at several other barrel ruptures and measuring the strength of the various barrel steels in the "hoop" direction as the barrel will always fail in hoop tension with a lengthwise crack. Any internally pressurized cylinder has 2X the force in the hoop direction as in the longitudinal (axial) dimension, so it's no wonder why barrels all seem to blow out with lengthwise cracks.


To my knowledge, no further analysis has been published, and if anyone here knows Zircon, please tell him I'd love to have his collection of barrels.

In the above picture, what has caused the rough surface on the top portion of the bore? Previously polished corrosion? Is that spot smooth or rough? I don't get to see the inside of a chamber from this angle and lighting very often, and they usually look to be pretty smooth from the vantage point of the end of the barrel. What I see in that picture appears to be small rings similar to what is visible after use of a Brush Research flex-hone if the bores have not been polished back to mirror. I looked at a 16ga Ideal Grade not too long ago that had opened chokes. The entire bore was mirror smooth from the chamber until the choke taper, at which point I could see the same tiny rings. I own a set of 16ga flex-hones, so I was familiar with the signature they leave behind. Again...I haven't seen many bores from this vantage point, so perhaps those ring marks are common, but it looks like the signature of a flex-hone. I am wrong about most things related to shotgun barrels, so that is likely also the case here. I'm asking the question for my own benefit, and not in an effort to offer up new information.

Drew:I remember when Zircon was posting his information on this site and have always wondered what happened to "the rest of the story". Would Dave Webber have contact in for Zircon?

I have sent several emails to Zircon trying to recover samples I sent to him long ago to no avail.

Does anybody know Zircon's name? Please don't post it if you do. But if someone knows his name perhaps they could send it to Drew or some other person here known to be affable and trustworthy.

Never mind, Drew informs me he already knows Zircon's name and had discussions with him two or three years ago.

It's ok Mike, still an interesting lead that was worth looking in to even though it seems to have fizzled out.

Really Mike?

Sure - PM Drew.

Drew hasn't communicated with Zircon since 2008 - six years.

Well, while you are at it, I would not mind the return of the 15 or so barrels I sent him.

Pete