Safe Practice to Consider

Terrym

Ah the wounded poster seeking revenge with trying to discredit.
You don’t even know what I do for a living and part of this is to assist engineers with their analyses for metal structural failure with NDT. Usually NDT is used to find conditions before a failure but can also assist in the evaluation of a failure.
You’ve already made an assumption of the failure and you aren’t even an engineer. Nor do you have a clue in this area. I don’t see you displaying any credibility here at all.
I’m no engineer but know how to find characteristics of a failure that an engineer seeks for evaluation.

MikePal

Yes the hole is considered as a weak point for two reasons.
One it is the thinnest area of solid material.
Two because of the stress riser condition where sharp geometrical change occurs in the metal such as a hole and threading does.
By plugging this hole with a threaded body you add re-enforcement again and reduce the bore pressure flexing attacking this weak area.

In case you are interested in the double split I approach a welding engineer who was also conversed in metallurgy with this phenomenon. His explanation was that when a barrel which is like a pressurized pipe begins to split the strongest area of stress would be approximately 180 degrees from the split and there would usually generate another tear. Depending on the material it could cause additional tearing and not limited to 2-splits.

Also the highest point of a rupture doesn’t always mean it started there but where the strongest pressure was felt.
I have no reason to doubt his years of training and experience.


Ed

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Originally Posted by ET1

Two because of the stress riser condition where sharp geometrical change occurs in the metal such as a hole and threading does.
By plugging this hole with a threaded body you add re-enforcement again and reduce the bore pressure flexing attacking this weak area.

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That actually make sense, crudely worded..the screw allows for the transfer of the flex.

All round, best to plug the hole for numerous reasons :)

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Originally Posted by ET1

In case you are interested in the double split I approach a welding engineer who was also conversed in metallurgy with this phenomenon. His explanation was that when a barrel which is like a pressurized pipe begins to split the strongest area of stress would be approximately 180 degrees from the split and there would usually generate another tear. Depending on the material it could cause additional tearing and not limited to 2-splits.

Ed

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I've never taken real note on barrel failures; when they split, I call them banana peel, is it predominantly 2 or 3 sections peeling back ?

edit add: Ed..I just re-watched that video I posted few days back....good example of the barrel failure with obstructions. I noticed the last one he did with the obstruction in the end (under the front sight) the barrel split into 4. It's hard to see where the splits are initiating/occurring.

https://www.youtube.com/watch?v=gmsBF6CXs18

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Originally Posted by MikePal

Mind you the screws would offer protection from moisture migrating into the hole causing further structural damage if the holes were not plugged, so yes I would not leave them open.

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MikePal

I fully agree that the holes should be protected from full exposure to the elements.
This would be a good additional reason to plug them.


Ed

Interesting....I googled the subject but was unable to find a scientific paper as to why a barrel is more prone to banana peeling versus exploding into shrapnel like a grenade (good thing they don't) when the powder charge encounters an obstruction and something must give way. My first thought was that the rifling somehow had something to do with it but that does not make any sense as it is a twist and the peel is linear. Also, I did witness a shotgun peeling with a muzzle plugged with mud. No rifling there! Can anyone provide a valid explanation?

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Originally Posted by ET1

Terrym

I’m no engineer but know how to find characteristics of a failure that an engineer seeks for evaluation.


Ed

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I'm no engineer either and the fact you deal with them doesn't really impress me. We consult with our lab routinely and it is staffed with Phd's and we deal with compressive strength and shear strength data for most of our products. So, none of this makes me an expert either.
What you haven't provided is a single disclaimer from any firearms manufacturer, barrel manufacturer, rifle sight manufacturer, to support your theory that drilled and tapped screw holes weaken a barrel to the point of failure. Interestingly you use a Savage ML10 to support your theory. That picture and many others have been around for a while and the screw holes are not ever mentioned as part of the law suits. Some barrels have the rear sights dove tailed into the barrel which removes an enormous amount of material compared to a screw hole yet we have never heard of this practice being potentially dangerous. Rifle actions are almost universally drilled and tapped for screw holes yet you don't hear about failures in actions and everybody knows how much the action absorbs pressure. Every single photograph I have ever seen of a blown up Savage ML10 has a failure of the barrel in front of the charge yet the breech is actually a hole and plug only held by threads but they never seem to fail. Also it has been proven that many of the owners of these catastrophic failures of Savage ML10's interestingly suffered no injury yet the damage of the gun should have caused serious injury. Do you think maybe they expected or intentionally wanted a blowup for litigation purposes?
Anyway, find me a gun manufacturer to substantiate your theory that screw holes can cause a rifle to fail.

The pressure is going to push through the least restrictive path, although the screw hole may be a stress riser putting a screw back in the hole would not change how the barrel would react. That being said, if you do not fill it and there is corrosion that would effect things a lot more than just having the screw hole there. With how these barrels are proofed the screw hole would not be the cause of the initial rupture but may end up in the path of the split due to the nature of a slightly weaker zone in the metal. Rifle barrels do seem to split on a twist, which makes sense with the rifling and the shotgun barrels opening up like a banana makes sense as well due to the consistency of the steel, since there is an obstruction in the barrel the pressure spikes and since all parts of the steel barrel are the same it will cause the rupture to be essentially uniform. I would not worry about your savage blowing up due to a screw hole not being filled, I would worry about putting a BP volume load of smokeless in the barrel, which was probably what caused this to happen.

Barrels will not shatter due to the nature of steel, it is not brittle. Steel fails by tearing, either by excessive force on an area or over time (fatigue). The great thing about steel is that you can build it thick enough to overcome both of these conditions, not so with aluminum, fatigue is always present in aluminum. Heating of the barrel can cause changes to the material as well, brazing on a sight, drilling holes and tapping all cause heat and if done too quickly and building up too much heat can change the material and weaken it is not treated properly afterwards.

Impact

I can only provide one plausible explanation from reasoning.
When we say hardening of barrel metal it is not super hardened. The more it is hardened the more brittle it would be if failure occurs. The level of hardness appears to allow it to keep some of its malleable properties to prevent fragmentation yet hold higher pressure than it would in its normal state of hardness.


Ed

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Originally Posted by Fox

The pressure is going to push through the least restrictive path, although the screw hole may be a stress riser putting a screw back in the hole would not change how the barrel would react. That being said, if you do not fill it and there is corrosion that would effect things a lot more than just having the screw hole there. With how these barrels are proofed the screw hole would not be the cause of the initial rupture but may end up in the path of the split due to the nature of a slightly weaker zone in the metal. Rifle barrels do seem to split on a twist, which makes sense with the rifling and the shotgun barrels opening up like a banana makes sense as well due to the consistency of the steel, since there is an obstruction in the barrel the pressure spikes and since all parts of the steel barrel are the same it will cause the rupture to be essentially uniform. I would not worry about your savage blowing up due to a screw hole not being filled, I would worry about putting a BP volume load of smokeless in the barrel, which was probably what caused this to happen.

Barrels will not shatter due to the nature of steel, it is not brittle. Steel fails by tearing, either by excessive force on an area or over time (fatigue). The great thing about steel is that you can build it thick enough to overcome both of these conditions, not so with aluminum, fatigue is always present in aluminum. Heating of the barrel can cause changes to the material as well, brazing on a sight, drilling holes and tapping all cause heat and if done too quickly and building up too much heat can change the material and weaken it is not treated properly afterwards.

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Very informative post, you seem to have expertise here. Getting back to the rust thing though, this example shown as evidence is a stainless steel barrel. What do you think are the odds of rust in a screw hole being sufficient to cause such a failure?

Terrym

My dealing with engineers and NDT training sure gives me more knowledge and understanding to work with metals.
I see you have trouble reading English because I never stated that drilled and threaded holes are the cause of failure. What I’m saying is to help avoid the possibility of the weakest area becoming an issue you can help ensure its integrity by keeping the thread hole filled with a screw.

Unlike you I make no claim to state where the failure originated because I’m not an engineer. You seem to have visions of being one to make certain evaluations.
For what reason are you mentioning action screws that usually are not exposed to bore pressure like sight screws?
Is this a diversionary tactic of including a non relevant condition.
If you replace removed material with additional of material like your rear dovetail sight where is the loss of material like an empty sight screw hole?
That was a lousy example.

Your welcome to try and impress others with your knowledge because the impression you have left with me is the lack thereof. Hey spout away if this makes you happy.


Ed