Think your Sunday is going badly? Look at my barrel..

[Lloyd]

Following this thread with lots of interest .

If you look closely at all the photographs , the bottom barrel has a double bulge in it , I thought this may have been caused by detonation due to an excess of oil left in the barrels ? Look closely and you can see that the lip of the choke in the bottom barrel has been torn and lifted ? Look at the choke removed from the top barrel , look at the mess that is all over it , that surely has never been caused with only a few shots through it since being thoroughly cleaned only the day before .

I am sorry but something just does not add up in this investigation .

I concur. Gasses are quite simple things. They always take the easy way out and expand to fill the available space. 

So in a sealed annular housing surround a a big gaping 18.whatever millimetre hole, how does gas cary so much dirt into such a confined and apparently sealed region? Unless of course that was at some point during a shot, that was an easy way out. Bearing in mind the ability of the gas as such a pressure it can and has caused steel to rupture

Its thin wall, but it’s not unusual in this respect and has been proven by independent testing at the proof house.

Again, I’d be curious to know about the radius at the change of cross section. I suspect it’s within design limits, but still curious.

It would be good to know (but prohibitively expensive to find out) about the metallurgical properties of the barrels in the region of failure. It could be neither Teague nor Ant are at fault. 

All this and more is academic though. 
For me, as a user of Teague, the real disappointment is in how this case was first and to a lesser extent handled by Teague/Westley Richards

 

[jwpzx9r]

Following this thread with lots of interest .

If you look closely at all the photographs , the bottom barrel has a double bulge in it , I thought this may have been caused by detonation due to an excess of oil left in the barrels ? Look closely and you can see that the lip of the choke in the bottom barrel has been torn and lifted ? Look at the choke removed from the top barrel , look at the mess that is all over it , that surely has never been caused with only a few shots through it since being thoroughly cleaned only the day before .

I am sorry but something just does not add up in this investigation .

Dieseling is a phenomenon that normally happens when an oil/air mixture is compressed in a close vessel though is it not?  I am sorry you are fantasizing here. The lead shot forced through the interface of the barrel and the choke tube is the critical thing for me because it goes before the wad and all of the gasses that follow. In that system the shot is passing the interface of the barrel and the choke tube before any extreme pressure is placed upon it is it not? The lead shot from the load has been force through between the barrel and the choke tube... that happened BEFORE the wad was passed the choke/ barrel interface.

 The barrel should easily be able to cope with any burning of an oil film left on the barrel walls behind the wad as it would also be able to cope with a dieseling event in front of the wad. 

I am not an engineer but this has nothing to do with a dieseling event ... something, almost certainly a wad, has caught the edge of the choke tube and raised it possibly the shot before the shot that actually caused the failure.

 

[jwpzx9r]

I concur. Gasses are quite simple things. They always take the easy way out and expand to fill the available space. 

So in a sealed annular housing surround a a big gaping 18.whatever millimetre hole, how does gas cary so much dirt into such a confined and apparently sealed region? Unless of course that was at some point during a shot, that was an easy way out. Bearing in mind the ability of the gas as such a pressure it can and has caused steel to rupture

Its thin wall, but it’s not unusual in this respect and has been proven by independent testing at the proof house.

Again, I’d be curious to know about the radius at the change of cross section. I suspect it’s within design limits, but still curious.

It would be good to know (but prohibitively expensive to find out) about the metallurgical properties of the barrels in the region of failure. It could be neither Teague nor Ant are at fault. 

All this and more is academic though. 
For me, as a user of Teague, the real disappointment is in how this case was first and to a lesser extent handled by Teague/Westley Richards

They are indeed BUT proofing a shotgun barrel is based on the premise of none plastic deformation. That is that when proofed the gun is subjected to up to 50 greater load than the design limits of the barrels in question and those design limits will be well in advance of what the proof house is going to subject them to and also a greater pressure than any available cartridge on sale would have... they have to be no manufacturer is going to have their barrels fail a proof test.

So we can discount faulty barrel materials the have passed a none plastic pressure test when they were tested by the proof house originally BUT they have been altered and all bets are off after that when it comes to the original barrel construction. I have to say this is only my opinion.

I concur. Gasses are quite simple things. They always take the easy way out and expand to fill the available space. 

So in a sealed annular housing surround a a big gaping 18.whatever millimetre hole, how does gas cary so much dirt into such a confined and apparently sealed region? Unless of course that was at some point during a shot, that was an easy way out. Bearing in mind the ability of the gas as such a pressure it can and has caused steel to rupture

Its thin wall, but it’s not unusual in this respect and has been proven by independent testing at the proof house.

Again, I’d be curious to know about the radius at the change of cross section. I suspect it’s within design limits, but still curious.

It would be good to know (but prohibitively expensive to find out) about the metallurgical properties of the barrels in the region of failure. It could be neither Teague nor Ant are at fault. 

All this and more is academic though. 
For me, as a user of Teague, the real disappointment is in how this case was first and to a lesser extent handled by Teague/Westley Richards

They are indeed BUT proofing a shotgun barrel is based on the premise of none plastic deformation. That is that when proofed the gun is subjected to up to 50 greater load than the design limits of the barrels in question and those design limits will be well in advance of what the proof house is going to subject them to and also a greater pressure than any available cartridge on sale would have... they have to be no manufacturer is going to have their barrels fail a proof test.

So we can discount faulty barrel materials the have passed a none plastic pressure test when they were tested by the proof house originally BUT they have been altered and all bets are off after that when it comes to the original barrel construction. I have to say this is only my opinion.

 

[jwpzx9r]

One thing that has not been addressed... could work carried out by a company who machine barrels to accept movable chokes lead to a plastic deformation immediately at the interface of the barrel /choke ? Personally ? I think it could IF there was even the smallest of gaps in that area. The barrel has been undeniably weakened by removal of metal from the barrel here which could have led to a deformation of the barrel which then allowed a wad to catch on the edge of the choke tube  damaging the barrel and the choke tube undetected by the shooter. Then on a subsequent firing of another shot the damaged choke allowed lead pellets and gasses to leading to what we see in the photographs supplied by the OP. 

I am not laying blame with anybody here but the above is my thoughts on what actually happened. Please remember if a wad has cleared the barrel and there has been no reason to think anything untoward had happened , which there would not be in the scenario I am putting forward, the shooter would simply reload and fire until the fateful shot was taken... or the damage was actually noticed.

 

[jwpzx9r]

It would be good to know (but prohibitively expensive to find out) about the metallurgical properties of the barrels in the region of failure. It could be neither Teague nor Ant are at fault. 

On this point I particularly call extreme BS ! If one examines the length of the choke tube and the area in which the damage has occurred.  All of the damage that has occurred within the length of the choke tube and barrel where the barrel that has been intrinsically or fundamentally weakened by removal of metal the manufacturer designed to be there to withstand the pressures  it specified ... if you are going to spout BS make it sensible BS.

 

[Guest]

is it possible that the extended chokes which I think were bought as a later addition (tell me if I am wrong) were made to the wrong bore spec , as 3800 were "standard" bore where as the 38 s were overbored, if per chance these chokes are a few thou to small that would explain the burnt grease(browning) on the undamaged choke and of course the failure.

    we are all human and as such open to making mistakes

 

[jwpzx9r]

is it possible that the extended chokes which I think were bought as a later addition (tell me if I am wrong) were made to the wrong bore spec , as 3800 were "standard" bore where as the 38 s were overbored, if per chance these chokes are a few thou to small that would explain the burnt grease(browning) on the undamaged choke and of course the failure.

    we are all human and as such open to making mistakes

The OP specified chokes made for his gun... they said they supplied them...  and why only one failure? Easy to find out though just measure it.. oh wait it has been destroyed

 

[Guest]

only teague make/supply replacement thin wall teagues...no argument there, and yes would be nice to get proof of measurements . 

 

[Luke_(NL)]

I also follow this thread with interest, but am a bit put off by terms akin to "extreme BS" and the repeated implications that Ant's story is "fishy". To the various theories I'd apply a certain old razor. Gas, dirt and even lead shot got wedged between outer barrel wall and choke tube. That means an opening existed for same to pass through. That opening may have been caused by several factors, but two options require the least supposition: Either the choke-to-barrel fit was fine, but wasn't screwed in right, or  the choke was screwed in fine, but the choke-to-barrel fit is faulty.

It's not my gun and I wasn't there, but there is no part about Ant's story that would seem "fishy" to me. Yet I'll also say that most human errors occur when people think they couldn't ever. But... What I find most surprising is that Teague has basically said that their measurements and cutting work, as well as their manufacturing are never off, without actual measurements of the bits involved to corroborate that, in this particular case. Given that something most definitely did go wrong, that's what I'd have expected if only to rule out future occurrence. 

 

[Lloyd]

On this point I particularly call extreme BS ! If one examines the length of the choke tube and the area in which the damage has occurred.  All of the damage that has occurred within the length of the choke tube and barrel where the barrel that has been intrinsically or fundamentally weakened by removal of metal the manufacturer designed to be there to withstand the pressures  it specified ... if you are going to spout BS make it sensible BS.

If you’re going to call be out as an extreme BS then you might want to provide extreme evidence to support your proposition. 
First of all, I qualified my statements as being academic. Maybe a better word would have been hypothetical. But I’d guess that would not satisfy here either. 
Secondly, you also qualified by stating you’re “not and engineer”. So I’d be interested to know how you are qualified to offer just your opinion but dismiss someone else’s ‘just their opinion’ with relative impunity and without robust cross examination or robust counter argument?

You have stated the metalwork around the choke is thin. Stating the obvious isn’t a skill beyond most folks to be honest. 

However, making yet further assumptions for the sake of further hypothesis for which there is really little point other than to flatter our own egos, mine included, I believe it’s fair to assume that Teague/Westley  Richards generally know what they’re doing in terms of design and manufacturing. You elude to this yourself in your comments regarding proofing. 

But this is the point you might have missed about the metallurgical properties of the barrels. Machining steel causes work hardening of the steel and dislocations at the micro structure. Some materials are worse than others for this. Stainless steel being one, copper another that spring immediately to mind. 

This alone effects the metallurgical properties but may well be within design limits under normal conditions. 
 

It could be. Let me stress that. It could be that during machining a tool was becoming dull. Thus work hardening becoming more likely and more work hardening creates more heat, more dulling of tool tip and more heat to effect the metallurgy of the steel... possibly, maybe, hypothetically speaking. 

Now this would normally result in process drift, seen in surface finish, dimensional and geometric tolerance. Could it be that an operator may have adjusted a machine setting to accommodate? Let’s assume not. Let’s assume 100% inspection rate of 100% of features. Can we also assume 100% guarantee that the barrels have been thoroughly checked right back to the mill certification, heat treatment certification and manufacturing certification? Let’s say yes. 

We could also say no and that would be equally valid in this context because the only facts we can guarantee is that neither you nor I or anybody else, perhaps even Teague/Westley Richards/Mirouku are in possession of all of the facts to make a fair and proper conclusion, thus all of this is conjecture. Is my conjecture inferior or BS as you put it? I’d argue no more or less than anyone else’s, including your diesling argument.

That said, I’m happy to be prooven wrong and learn something 

 

[El Spavo]

Girls, girls!... you're both pretty!

 

[Lloyd]

Girls, girls!... you're both pretty!

I get this often. I blame autocorrect. 
it’s spelt ‘p e t t y’

 

[Robden]

Now I'm probably talking BS, but could the barrel be xrayed, and measurements taken of the threaded section from that?

 

[jwpzx9r]

Now I'm probably talking BS, but could the barrel be xrayed, and measurements taken of the threaded section from that?

I do not think you are talking BS what you are saying could be done... at some cost by a laboratory.

If you’re going to call be out as an extreme BS then you might want to provide extreme evidence to support your proposition. 
First of all, I qualified my statements as being academic. Maybe a better word would have been hypothetical. But I’d guess that would not satisfy here either. 
Secondly, you also qualified by stating you’re “not and engineer”. So I’d be interested to know how you are qualified to offer just your opinion but dismiss someone else’s ‘just their opinion’ with relative impunity and without robust cross examination or robust counter argument?

You have stated the metalwork around the choke is thin. Stating the obvious isn’t a skill beyond most folks to be honest. 

However, making yet further assumptions for the sake of further hypothesis for which there is really little point other than to flatter our own egos, mine included, I believe it’s fair to assume that Teague/Westley  Richards generally know what they’re doing in terms of design and manufacturing. You elude to this yourself in your comments regarding proofing. 

But this is the point you might have missed about the metallurgical properties of the barrels. Machining steel causes work hardening of the steel and dislocations at the micro structure. Some materials are worse than others for this. Stainless steel being one, copper another that spring immediately to mind. 

This alone effects the metallurgical properties but may well be within design limits under normal conditions. 
 

It could be. Let me stress that. It could be that during machining a tool was becoming dull. Thus work hardening becoming more likely and more work hardening creates more heat, more dulling of tool tip and more heat to effect the metallurgy of the steel... possibly, maybe, hypothetically speaking. 

Now this would normally result in process drift, seen in surface finish, dimensional and geometric tolerance. Could it be that an operator may have adjusted a machine setting to accommodate? Let’s assume not. Let’s assume 100% inspection rate of 100% of features. Can we also assume 100% guarantee that the barrels have been thoroughly checked right back to the mill certification, heat treatment certification and manufacturing certification? Let’s say yes. 

We could also say no and that would be equally valid in this context because the only facts we can guarantee is that neither you nor I or anybody else, perhaps even Teague/Westley Richards/Mirouku are in possession of all of the facts to make a fair and proper conclusion, thus all of this is conjecture. Is my conjecture inferior or BS as you put it? I’d argue no more or less than anyone else’s, including your diesling argument.

That said, I’m happy to be prooven wrong and learn something 

To be honest what a lot of total bluster! 

Here is a fact. The makers of that barrel took a rod of steel with a certain tensile strength... lets say for argument sake 250 tonnes / cm2 I have no real idea what the real figure is. They take that rod of steel and the bore a hole through the center of it... the material that is left still has the same tensile strength as before it was bored out. The manufacturers made that barrel with a wall thickness they calculated was required to withstand a pressure well in excess of anything that in normal use would cause it to fracture and with a degree of certainty that they the company have established through their own making and testing of many barrels.

Since then another engineering company has reduced that wall thickness considerable to allow it to accept movable chokes the barrel greatly reducing the wall thickness and thus its ability to withstand the pressure of the original design. The barrel has subsequently failed in the exact area in which they plied their trade and reduced the pressure resistance of that barrel... and you are questioning the metallurgy of the metal ???

I again state if you are going to post BS make it sensible BS !

 

[jwpzx9r]

I also follow this thread with interest, but am a bit put off by terms akin to "extreme BS" and the repeated implications that Ant's story is "fishy". To the various theories I'd apply a certain old razor. Gas, dirt and even lead shot got wedged between outer barrel wall and choke tube. That means an opening existed for same to pass through. That opening may have been caused by several factors, but two options require the least supposition: Either the choke-to-barrel fit was fine, but wasn't screwed in right, or  the choke was screwed in fine, but the choke-to-barrel fit is faulty.

It's not my gun and I wasn't there, but there is no part about Ant's story that would seem "fishy" to me. Yet I'll also say that most human errors occur when people think they couldn't ever. But... What I find most surprising is that Teague has basically said that their measurements and cutting work, as well as their manufacturing are never off, without actual measurements of the bits involved to corroborate that, in this particular case. Given that something most definitely did go wrong, that's what I'd have expected if only to rule out future occurrence. 

I could not agree more! The fact of the matter is that the barrels of the gun have been altered from the original specification by a respected engineering company. The thing for me is that just because they are such a company does not mean that mistakes could not be made, and this has been the tenor of my posting from the get go. 

My personal point of view is that you have work of this nature done at your own risk. I say this because the work done without doubt reduces the ability of the barrels to withstand the manufacturer design pressure of the barrel . Further more the owner of the gun is then left open to the question were the barrels kept clean in the vital area and were the chokes properly seated... just as has been stated by the engineering company that did the work. It is very difficult for the OP to win his case without a complete forensic analysis of the barrels... have you any idea of the costs of that? Eye watering I suspect.

 

[Lloyd]

@jwpzx9r

Youre demonstrating a considerable about of bluster yourself here and being somewhat contradictory and could be taken even as inflammatory. 
 

you’re claim makes that the barrel manufacturing is carefully designed and processed and whose safety is essentially guaranteed, whereas the modification is by your wording rendered a near reckless  affair.

whilest not explicit there is an implied lack of competency on the part of the modification. My point being that first of all, manufacturing defects are not limited to modifications and can and do on a regular basis effect OEM and secondly, the modification has been carried out by a company of long standing g shoes work has stood up to scrutiny over many previous occurrences.

For reference the material most manufacturers use for barrel making would be the old BS EN (no BS pun intended) designation EN40B (722M24) a Crome Molybdenum nitriding steel as specified by the NATO small arms directive with a UTS (strength) of some 700 - 1000 N/mm2. This material would often undergoe a fair amount of post machining processes including stress reliving, a process which your presumed gun drilling operation (the process of drilling holes of very deep aspect ratios) has omitted to take into consideration and a process that significantly effects the metallurgical properties of the material in cloves. Further hear treatment processing of hardening the core and case hardening by nitriding, also omitted by your synopsis.

Again, if you’re going to call someone out on BS then you might be better placed if you limit your own BS. This is all a matter of subjective opinion on the part of all commentators here, yours and mine included. 

 

[jwpzx9r]

@jwpzx9r

Youre demonstrating a considerable about of bluster yourself here and being somewhat contradictory and could be taken even as inflammatory. 
 

you’re claim makes that the barrel manufacturing is carefully designed and processed and whose safety is essentially guaranteed, whereas the modification is by your wording rendered a near reckless  affair.

whilest not explicit there is an implied lack of competency on the part of the modification. My point being that first of all, manufacturing defects are not limited to modifications and can and do on a regular basis effect OEM and secondly, the modification has been carried out by a company of long standing g shoes work has stood up to scrutiny over many previous occurrences.

For reference the material most manufacturers use for barrel making would be the old BS EN (no BS pun intended) designation EN40B (722M24) a Crome Molybdenum nitriding steel as specified by the NATO small arms directive with a UTS (strength) of some 700 - 1000 N/mm2. This material would often undergoe a fair amount of post machining processes including stress reliving, a process which your presumed gun drilling operation (the process of drilling holes of very deep aspect ratios) has omitted to take into consideration and a process that significantly effects the metallurgical properties of the material in cloves. Further hear treatment processing of hardening the core and case hardening by nitriding, also omitted by your synopsis.

Again, if you’re going to call someone out on BS then you might be better placed if you limit your own BS. This is all a matter of subjective opinion on the part of all commentators here, yours and mine included. 

I cannot understand why you are posting the above rubbish. You are stating I made a  " synopsis " all I have stated is that the manufacturers of those barrels designed them to be a certain wall thickness and operate within a working load that they have found to be adequately ensure the barrels will not fracture using any available ammunition and to easily pass a proof test of their stated safe working pressure.

I am sorry you can quote as many standards of steel used by the manufacturers as you like. The simple fact you seem to be willing to ignore is that the makers of that barrel designed it WITHIN the safe working limits of the material they chose to use and that the safety standards the apply are up to standard. Further more I have made no claim for the manufacturing process other than to state that the barrel manufacturers know what they are doing.

What you have done for some reason is to state a set of conditions where the manufacturer of the barrels could have been shoddy in their work. Do you honestly think that they do not know about every condition you have stated above and take steps to ensure their product is produced to safeguard against this happening, in short do not believe the have expert metallurgists working on their behalf ?

But let us not get bogged down in the BS you have quoted above the fact is these barrels failed exactly where the engineering company tasked with the work altered the wall thickness of these barrels greatly from those specified by the original makers... and you want the metal in this area tested ... why?

 

[Lloyd]

@jwpzx9r

The ‘fact’ is neither you and certainly not I are in possession of the full ‘facts’

it is a ‘fact’ that you claim “Here is a fact. The makers of that barrel took a rod of steel with a certain tensile strength... lets say for argument sake 250 tonnes / cm2 I have no real idea [fact] what the real figure is.

I in fact do have an idea what the material is and have stated so in  the above. 
 

You are in ‘fact’ at least correct that at least some shotgun barrels are made by drilling steel stock. I can support your ‘fact’ but the ‘fact’ I have witnessed this myself on a tour of a shotgun manufacturer’s facilities and seen this for myself. However it is also a ‘fact’ the shotgun barrels are made tubular by other means. This ‘fact’ is easily verifiable. It is a ‘fact’ however that I do not know the manufacturing process used by mirouku and I make the ‘presumption’ that neither do you. If in which case this is true, your ‘fact’ is this in ‘fact’ not a ‘fact’ at all and is mere supposition.

I further ‘presume’ you are also not intimate  with the design calculations, testing and manufacturing /modification processes of Teague and again if this is ‘factual’ you are then in ‘fact’ in no real position to make an even remotely qualified comment as to the competency of Teague and I may ‘suppose’ Teague could take great umbrage at your postulation.
 

So for a little more bluster and BS can we perhaps assume that Teague have tested their modification via a proofing house on at least one occasion? You could assume this would be in Teague  interest to assure their modification offering has been designed and manufactured to be safe. You’d be a braver man than me to claim otherwise, though you have certainly been brave enough to imply it!

So, let’s assume the 722M24 material has been hardened to the T condition  (most typical) heat treatment of quench hardening and tempering of this material grade. Shall we assume that our impeccable manufacturing and design specifications of the barrel manufacturer has stress relived the materials post machining operations and the barrels have also been case hardend by nitriding  to the correct depth (to within a tolerance of course, after all, heat treatment of  steels isn’t super precise process) This gives a supposed tensile strength of 1000N/mm^2

Shall we assume our barrels measure 18.6mm bore with an outside diameter of say 21mm?

This would give us a designed wall thickness resulting in a cross sectional area of 75mm^2

Fortunaley for us, bar easily translates to Newtons/mm^2 but hose Newton’s are a devilishly difficult thing to relate to so dividing by the gravitational constant we have a number of kilograms load the barrels are capable of taking before breaking. Not yeliding, but breaking. This come out in round figures of 7,600kg or 7.6 tonnes if you prefer. 

Now, working pressure of a typical cartridge may be 600bar and proof would be +25% would equate to 60N/mm^2 x 1.25 giving a pressure of 75N/mm^2 

Our 18.6mm bore would give us an area of 270mm^2 (rounded) x by 75N/mm^2 pressure at proof gives 20.25kN divide this by the gravitas constant of 9.81. Call it 10 and we have a load on the manufacture designed barrel of 20tonnes

Oops! 
 

Could be missing some vital ‘facts’ here. Well, of course we are. We all are. But you know, the standard is of course to blow a lot of hot air in such discipline. Seems also that you only need put forward a few ‘facts’ or just claim them to be and this give permission to claim other folks argument are bluster and BS

so yeah. I can get behind that. 

So @jwpzx9r you’re full of BS and bluster. Apparently this is a ‘fact’

 

[MartynB]

Put simply only two things damage  guns at the muzzle , either the muzzle is blocked or the choke isn’t seated  The why’s and wherefore of that happening in Ant’s case have all been covered 

 I’d actually say it’s a testament to Teague’s low profile thread system , and to Miroku’s  barrel steel , that the choke tube didn’t launch into the next county or the barrel split like a Bugs Bunny cartoon .  Out of interest Miroku  made the barrels for all Browning  1/ 3/4/5/725 guns , all the Miroku variants, and they even make a Miroku for the Aussies which is supplied with a Briley thin wall system ( We don’t get it for marketing reasons )  .  Miroku also supply barrel making machines to other gunmakers .
 
Whatever happened to Ant’s gun isn’t going to stop me using my twoTeague converted  Miroku’s and it won’t stop me sending a third . What is interesting to me is the power of the internet , as I’m pretty sure that Ant publicising the failure was responsible for the ‘ without prejudice ‘ solution that he has been offered . 

 

[jwpzx9r]

@Lloyd

What the hell is wrong with you? You are creating circumstances to fit your own narrative and it is not relevant to anything I have posted.

I have merely pointed out that the makers of that barrel designed and used materials they thought appropriate to satisfy their own standards and easily surpass those of the proof house when testing their stated safe maximum working pressure.

Those barrels have then been re-worked by another party and failed in the exact area that they did their work and you for some reason would like to know about the metallurgy in that area. I am making an assumption that, given you have said in your post that neither the OP nor Teague may be the reason for the failure, you are pointing at a problem with the metal structure in this area? If this is the case I beg to differ with that opinion. Metal that the barrel manufacturer thought was intrinsic to the safe functioning of those barrels has been removed and this would be any engineers's  primary conclusion. However notwithstanding this even if the metal in that area had structural abnormality it does not mean that the barrel would have fractured had the metal that the designers said should be present had not been removed , it is common sense all manufacturers build in a safety factor.

It matters not what Teague think that safety factor is the manufacturers of the barrels have set the standard for that and you mess with that at your peril .

For the record I think as I have already stated that the reason the damage occurred is down to something,almost certainly a wad, catching the edge of that choke tube and resulting in the wad forcing lead shot between the barrel and the choke tube as can be seen by lead pellets extruded through past the threads of the choke tube... that the barrel survived that event without rupture is in fact testament to the strength of the metal in that area not a weakness ! Even though it has been considerably weakened by removal of metal .