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Double Rifles, Single Shots & Combinations >> Double Rifles

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DarylS
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Re: OSR, Double Damage and Barnes' Response [Re: tinker]
      #152023 - 27/01/10 02:52 PM

Excellent post, 404Bearslayer.

--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V


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4seventy
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Re: OSR, Double Damage and Barnes' Response [Re: tinker]
      #152028 - 27/01/10 03:10 PM

Quote:

There are metal deposition (spray) processes which can leave the appearance of brimstone, local to the area of affect.





Good point.


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404bearslayer
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Re: OSR, Double Damage and Barnes' Response [Re: 4seventy]
      #152036 - 27/01/10 07:35 PM

4seventy & tinker,

thanks for the advice on the 'brimstone' appearance' . Maybe I used a misleading term here. What I wanted to describe is the look of 'burnt' metal. When you overheat metal long enough, it 1) becomes first softer then brittle in the end 2) the surface assumes a typical look because iron oxide builds up - the surface is no longer shiny, but rather dull, 'dry' - maybe 'brimstone' was too strong an image here, initially I wanted to call it a 'shale-like' appearance .

Daryl,

thanks. You made one of the most important points in this tread regarding obturation, which I'd like to take the chance to expand on a little:

Obturation:

A bullet, by being pushed fast enough, get slightly compressed (inertia effect) while it travels through the barrel, which temporarily expands its diameter. This is a however a known and beneficial process that aids the sealing of the bullet in the barrel. Without that, we would have gas leakage as the barrel, being elastic, expands temporarily as well while under pressure (this is why strain gauges can measure pressure). THIS is what obturation means, it is a word with a latin root that means to seal. Obviously, a SOFTER bullet obturates (seals) better then a hard bullet, as softer material is more easily compressed (again: LENGTHWISE compression, because the inertia of the bullet works against its acceleration, which means the diameter of the bullet increases). So harder bullets are by definition LESS prone to that effect. Herein lies the real problem of these bullets: As manufacturers undersize 'hard' bullets to minimize pressure spikes at ignition, they open the window for potentially damaging gas leakage. These leakages, which amplify the gas flow in areas where they occur (in the sense of a jet stream), could over time be damaging to the inside of a barrel. Think of miniature blow-torches passing through those leaks - I think you get the idea.


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450_366
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Re: OSR, Double Damage and Barnes' Response [Re: tinker]
      #152040 - 27/01/10 08:41 PM

Quote:

There are metal deposition (spray) processes which can leave the appearance of brimstone, local to the area of affect.

Depending on the parent materials, the end result can give a very very tough and hard surface that can be machined/ground/finished.





Cheers
Tinker




Are you refering to the powder spraygun that uses a oxy/acetylene flame.
In the industry its often applied on moving parts that needs a bit of buildup after wear, it could explain the surface. I would be damn more easy to just use a hammer to bend the bites and lug up a bit then using a torch.

But there are some really stupid beople out there so who knows

--------------------
Andreas

"Yeas it kicks like a mule he said, but always remember that its much worse standing on the other end"


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akjeff
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Re: OSR, Double Damage and Barnes' Response [Re: 450_366]
      #152081 - 28/01/10 01:09 PM

This OSR phenomenon that's referred to. Is it visible down the length of the barrel? If so, I have a hard time accepting that it's caused by the bullet. Even a "hard" bullet like a mono solid. You take a solid copper bullet, banded or otherwise. When that sucker hits the rifling in a considerably harder steel barrel, it will swage down to bore dimensions in pretty short order. Metal has to move period, or it would be a bore obstruction. Once the initial swaging is done, I fail to see how it could act on the barrel any differently than any other bullet, for the remainder of it's trip down the bore. Fire a conventional solid, and a monometal solid down the same bore, and measure them. See if there's a difference in the land/groove dimensions?

Jeff


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450_366
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Re: OSR, Double Damage and Barnes' Response [Re: akjeff]
      #152098 - 28/01/10 09:16 PM

Quote:

This OSR phenomenon that's referred to. Is it visible down the length of the barrel? If so, I have a hard time accepting that it's caused by the bullet. Even a "hard" bullet like a mono solid. You take a solid copper bullet, banded or otherwise. When that sucker hits the rifling in a considerably harder steel barrel, it will swage down to bore dimensions in pretty short order. Metal has to move period, or it would be a bore obstruction. Once the initial swaging is done, I fail to see how it could act on the barrel any differently than any other bullet, for the remainder of it's trip down the bore. Fire a conventional solid, and a monometal solid down the same bore, and measure them. See if there's a difference in the land/groove dimensions?

Jeff




I think 404bearslayer made a good point that its most likely not the bullet that is the couse of osr, than the pressure within the barrel behind the bullet. But then it needs to be really high all the way down and exact so it affects the steel in an uniform way so the rifling appears to be equal affected over the lenght of the barrel.

--------------------
Andreas

"Yeas it kicks like a mule he said, but always remember that its much worse standing on the other end"


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470evans
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Re: OSR, Double Damage and Barnes' Response [Re: akjeff]
      #152101 - 28/01/10 11:19 PM

Quote:

This OSR phenomenon that's referred to. Is it visible down the length of the barrel? If so, I have a hard time accepting that it's caused by the bullet. Even a "hard" bullet like a mono solid. You take a solid copper bullet, banded or otherwise. When that sucker hits the rifling in a considerably harder steel barrel, it will swage down to bore dimensions in pretty short order. Metal has to move period, or it would be a bore obstruction. Once the initial swaging is done, I fail to see how it could act on the barrel any differently than any other bullet, for the remainder of it's trip down the bore. Fire a conventional solid, and a monometal solid down the same bore, and measure them. See if there's a difference in the land/groove dimensions?

Jeff




The doubles I have seen with OSR (4-5), including one of my own, begin to exhibit the OSR about 8-10 inches down the barrels and the OSR continues to the muzzle. It appears where the barrels are beginning to taper down. There is too much steel in the chamber end for it to show. The more severe the OSR the further up the barrels it will begin.


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404bearslayer
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Re: OSR, Double Damage and Barnes' Response [Re: 470evans]
      #152103 - 29/01/10 01:05 AM

470evans,

that what you see is only apparent towards the muzzle has something to do with the fact that your gun is tapered - the closer you come to the muzzle, the weaker the barrel becomes.

Now, whatever I have read here about what some people call OSR are classical signs of a barrel that has been exposed to a level of pressure that has expanded it to a point where it cannot spring back fully to what it was before. Even what some people call a test for OSR (looking inside that barrel at a angle) is a classical test for that with gunsmiths in my country. Now, as I pointed out before, hard bullets can create far steeper pressure curves then other bullets, add to that a round where the bullet's ogive accidentally touches the rifling (had that with factory ammo in my .404 quite often) and you can have such a rapid rise in pressure that older softer steels, especially in thin barrels, cannot spring back fully anymore. And don't forget that some barrels are duds, they might not have been hardened correctly in manufacturing to begin with. With benign loads (and by that I mean a shallow rise in pressure, rather then a weak load per se) this might never be an issue. With a steep pressure curve, however, it will bring out faults.

As for the claimed 'shadows' of lands showing outside the barrel and the like: That is an easily understood phenomenon, and has nothing to do with a bullet pressing out the lands. Imagine a barrel that is cut open lengthwise and rolled out before you. What do you see? Something like the profile of a car tire, the lands stand out, the deeper the grooves are cut the more the barrel has a 'profile'. Now imagine you could tear like the Hulk at the sides of this rolled-out barrel (this represents excessive pressure). The grooves, being cut into the barrel, are the weakest link (the barrel is thicker where the lands remain) - therefore the weakest link (the grooves) will stretch first (but certainly differently, -this for people who now start thinking about cut-rifling versus hammer-forged). Do this with enough force and you will see the claimed OSR shadows on the outside of the barrel. They are simply stretch-marks alternating with stronger sections of the barrel. Hence the visible lands / grooves pattern.

Edited by 404bearslayer (29/01/10 01:08 AM)


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9.3x57
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Re: OSR, Double Damage and Barnes' Response [Re: 404bearslayer]
      #152104 - 29/01/10 01:21 AM

Quote:

As for the claimed 'shadows' of lands showing outside the barrel and the like: Do this with enough force and you will see the claimed OSR shadows on the outside of the barrel. They are simply stretch-marks alternating with stronger sections of the barrel. Hence the visible lands / grooves pattern.




I've wondered about this for a long time, namely; Is it truly the lands pressed out, or, rather the weak part of the barrel in the grooves that is "giving way". I suspect it is the latter. Not sure.

--------------------
What are the Rosary, the Cross or the Crucifix other than tools to help maintain the fortress of our faith in Jesus Christ, the Son of God?


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DarylS
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Re: OSR, Double Damage and Barnes' Response [Re: 404bearslayer]
      #152114 - 29/01/10 04:22 AM

Quote:

470evans,
The grooves, being cut into the barrel, are the weakest link (the barrel is thicker where the lands remain) - therefore the weakest link (the grooves) will stretch first (but certainly differently, -this for people who now start thinking about cut-rifling versus hammer-forged). Do this with enough force and you will see the claimed OSR shadows on the outside of the barrel. They are simply stretch-marks alternating with stronger sections of the barrel. Hence the visible lands / grooves pattern.




Spot-on, 470 and 9.3 - I now see the 'light'. I was definitiely having trouble with the lands being pushed to the outside hypothesis.

--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V


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4seventy
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Re: OSR, Double Damage and Barnes' Response [Re: 9.3x57]
      #152121 - 29/01/10 08:44 AM

Quote:

Quote:

As for the claimed 'shadows' of lands showing outside the barrel and the like: Do this with enough force and you will see the claimed OSR shadows on the outside of the barrel. They are simply stretch-marks alternating with stronger sections of the barrel. Hence the visible lands / grooves pattern.




I've wondered about this for a long time, namely; Is it truly the lands pressed out, or, rather the weak part of the barrel in the grooves that is "giving way". I suspect it is the latter. Not sure.




Yes, the stretch mark theory has been around for quite some time, and is indeed a plausable one.
However, it doesn't answer the really important questions concerning OSR.
The true cause is still a mystery.

There are other factors involved here though which have not yet been discussed in any of the threads concerning OSR.


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AkMike
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Re: OSR, Double Damage and Barnes' Response [Re: 4seventy]
      #152158 - 29/01/10 07:00 PM

One factor that hasn't been brought up is that the DR tubes have a much thinner sidewall than a bolt gun. I am not an expert, but I can easily see that being a serious factor.


What say ye?

--------------------
"When you see that in order to produce, you need to obtain permission from men who produce nothing; when you see that money is flowing to those who deal not in goods, but in favors; you may know that your society is doomed." Ayn Rand


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DarylS
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Re: OSR, Double Damage and Barnes' Response [Re: AkMike]
      #152175 - 30/01/10 01:10 AM

Unfortunately, the true cause is most likely a combination of many contributing factors which most likely change, gun to gun.

--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V


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akjeff
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Re: OSR, Double Damage and Barnes' Response [Re: AkMike]
      #152184 - 30/01/10 02:16 AM

Quote:

One factor that hasn't been brought up is that the DR tubes have a much thinner sidewall than a bolt gun. I am not an expert, but I can easily see that being a serious factor.


What say ye?




The reason I have doubts about the thin barrel wall theory is that I think the bullet would have to be swaged down upon entering the bore, which occurs in the heavier walled shank of the chamber area. By the time it gets to the thin walled part of the barrel, I should think the bullet is already at bore dimension, and thus, have no impact on causing the tubes to "bulge". If the bullet were truly causing a "bulge" that travels down the exterior of the barrel, the chamber pressure would be sky high, and would have to remain higher than normal, for the entire time that it's in the barrel. But, that's just my opinion.

I should think the whole thing should be easily(but not cheaply!) proved/disproved by attaching strain gages inch by inch down a test barrel contoured like a double rifle. Fire some control rounds of conventional lead cored bullets, and then fire the mono's, and see what really happens.

Jeff


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tinker
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Re: OSR, Double Damage and Barnes' Response [Re: akjeff]
      #152187 - 30/01/10 03:20 AM

I grew up (active in the shops from 8+years old) in top-shelf auto restoration shops, doing full-kit jobs on best-placing Concours show cars.

I've seen a lot of fine metal beaten in every conceivable direction -- with every imaginable kind of hammer...


...which brings the hammer to the conversation.
The hammer I'm speaking of here/now is the bullet.

Anyone here ever own a vintage Ferrari?
Do y'all know what the tool kit looks like for a top shelf street roadster?
One thing you'll see in there is a big lead hammer.
That big lead hammer is your lug-wrench for wheel removal/replacement.
That big lead hammer is what the factory prescribes as the ideal tool for knocking the knockoff (single central) wheel nuts loose.

Try the same operation with a hard copper or cupric alloy wrench, and you'll likely end up screwing up the finish on the spinner nuts.


Could it be possible that this dead VS springy nature of the bullet material could have something to do with the phenomenon?



Just thinking...





Cheers
Tinker

--------------------
--Self-Appointed Colonel, DRSS--



"It IS a dangerous game, and so named for a reason, and you can't play from the keyboard. " --Some Old Texan...


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450_366
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Re: OSR, Double Damage and Barnes' Response [Re: tinker]
      #152193 - 30/01/10 06:19 AM

Quote:

I grew up (active in the shops from 8+years old) in top-shelf auto restoration shops, doing full-kit jobs on best-placing Concours show cars.

I've seen a lot of fine metal beaten in every conceivable direction -- with every imaginable kind of hammer...


...which brings the hammer to the conversation.
The hammer I'm speaking of here/now is the bullet.

Anyone here ever own a vintage Ferrari?
Do y'all know what the tool kit looks like for a top shelf street roadster?
One thing you'll see in there is a big lead hammer.
That big lead hammer is your lug-wrench for wheel removal/replacement.
That big lead hammer is what the factory prescribes as the ideal tool for knocking the knockoff (single central) wheel nuts loose.

Try the same operation with a hard copper or cupric alloy wrench, and you'll likely end up screwing up the finish on the spinner nuts.


Could it be possible that this dead VS springy nature of the bullet material could have something to do with the phenomenon?



Just thinking...





Cheers
Tinker




And the steel jacket fms? That supposely not contribute to the osr fenomen?
And a large peace of oak works to, but takes up to much space in the trunk.

--------------------
Andreas

"Yeas it kicks like a mule he said, but always remember that its much worse standing on the other end"


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404bearslayer
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Re: OSR, Double Damage and Barnes' Response [Re: tinker]
      #152194 - 30/01/10 06:33 AM


Tinker,

your ideas about a hammer are useful. Let's first remember the main claim about OSR: 'A hard bullet presses the rifling from the inside to the outside, while a soft bullet does not do so'. Let's play 'Mythbusters' and set up the following experiment: Take a potato, cut it in half, and then carve a heart into it. The potato is the barrel, the heart represents the rifling. Now take a hammer (which represents the hard bullet) and violate the potato with some strikes. Now turn the potato around and look for the heart being visible on the other side. You won't find any pattern, irregardless of whether you strike the potato with a hammer or a bag of feathers. The reason is simple and shows the main fallacy of the OSR claim: No force or material on earth can drive a profile through a material that is of the same hardness and consistency as the profile itself. Take another cut potato and put a little wooden heart on it, hammer the wooden heart into the potato. Now turn the potato around and you will see the heart shape imprinted on the other side. Hence, OSR could only occur if grooves and lands were made of different materials with significanty different levels of hardness.


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srose
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Re: OSR, Double Damage and Barnes' Response [Re: 404bearslayer]
      #152199 - 30/01/10 07:02 AM

Isn't the bullet your wooden heart?

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470evans
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Re: OSR, Double Damage and Barnes' Response [Re: 404bearslayer]
      #152202 - 30/01/10 08:04 AM

Quote:


Tinker,

your ideas about a hammer are useful. Let's first remember the main claim about OSR: 'A hard bullet presses the rifling from the inside to the outside, while a soft bullet does not do so'. Let's play 'Mythbusters' and set up the following experiment: Take a potato, cut it in half, and then carve a heart into it. The potato is the barrel, the heart represents the rifling. Now take a hammer (which represents the hard bullet) and violate the potato with some strikes. Now turn the potato around and look for the heart being visible on the other side. You won't find any pattern, irregardless of whether you strike the potato with a hammer or a bag of feathers. The reason is simple and shows the main fallacy of the OSR claim: No force or material on earth can drive a profile through a material that is of the same hardness and consistency as the profile itself. Take another cut potato and put a little wooden heart on it, hammer the wooden heart into the potato. Now turn the potato around and you will see the heart shape imprinted on the other side. Hence, OSR could only occur if grooves and lands were made of different materials with significanty different levels of hardness.




404, I must be losing something in translation here. I would guess you have never seen OSR either?

Unless you've seen it it's very difficult to explain and get some people to believe it even exists. At least one non-believer(Cal)has changed his tune about it existing.

Cal, I hope you don't find any issues with that beautiful Wilkes. I'd like to hear what you find out after you inspect the rifle and I look forward to hearing there aren't any issues.


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4seventy
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Re: OSR, Double Damage and Barnes' Response [Re: AkMike]
      #152210 - 30/01/10 11:04 AM

Quote:

One factor that hasn't been brought up is that the DR tubes have a much thinner sidewall than a bolt gun. I am not an expert, but I can easily see that being a serious factor.


What say ye?




Mike,
You are correct that the thin barrel walls are a very relevant issue concerning OSR.
This is nothing new though, and has been mentioned before in this thread and others relating to OSR.

400NE had this to say back on page one of this thread.
Quote:

OSR is the result of the expansion of the necessarily thin walls of double rifle barrels




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AkMike
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Re: OSR, Double Damage and Barnes' Response [Re: 4seventy]
      #152212 - 30/01/10 11:32 AM

Whoopps I didn't see that post!
I think that the mono is engraved through out the length of the barrel. From what I gather (not having seen one) it's more pronounced further out towards the business end.

--------------------
"When you see that in order to produce, you need to obtain permission from men who produce nothing; when you see that money is flowing to those who deal not in goods, but in favors; you may know that your society is doomed." Ayn Rand


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404bearslayer
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Re: OSR, Double Damage and Barnes' Response [Re: AkMike]
      #152263 - 30/01/10 11:03 PM

470EVANS,

there is nothing lost in translation here - and if, it would be the fault of your fellow Texans, as I went to college in the Lone Star State (and later to grad school in Florida) and had that kind of English imprinted on me . If anything, I might have picked up an accent .

I simply addressed one of the wilder claims about HOW OSR comes about. I know perfectly well what people talk about, and do not have reason to believe that they lie about their observations. The problem is that few have an understanding of internal ballistics and arrive at fairly wild conclusions about the processes that lead to those manifestations. I have explained most of the processes and misconceptions within this thread. For people who prefer the opinion of a specialist: In Australia, I would talk to an engineer at Thales/ADI, in Europe, you want to talk to the folks at BOFORS, Sweden (Thales/ADI makes the powder for Hodgdon, Bofor makes the powder for Alliant, Norma, Rottweil). These people know ballistics at the professional level, it is part of their job description. Don't expect this level of expertise within even the larger bullet companies - they simply don't need to know - and for the most part they don't.

Edited by 404bearslayer (30/01/10 11:10 PM)


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Paul
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Re: OSR, Double Damage and Barnes' Response [Re: 404bearslayer]
      #152269 - 31/01/10 12:22 AM

404, I can't see that potato 'flesh' and steel comparison really works. Raw potato can't be bent into different shapes that will retain any strength but steel often can. Without cooking and mashing a spud there is no way it can be forged into different shapes the way steel can.

Risking another false analogy, the pattern left on the outside of hammer-forge-rifled barrels shows that patterns emanating from inside the tube can be seen outside.

Akjeff, I've thought about your point, too. I seem to remember reading somewhere that firearm barrels can bulge as projectiles go through them and contract again, anyway, like a a snake digesting a mouse. This sounds hard to believe, especially because it might affect the solder in double guns and rifles, but maybe some of these mono bullets don't just shear off the offending bits of driving band as they hit the rifling but cause more than the allowable stress all the way up the barrel.

- Paul


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450_366
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Re: OSR, Double Damage and Barnes' Response [Re: Paul]
      #152273 - 31/01/10 01:16 AM

Quote:

Risking another false analogy, the pattern left on the outside of hammer-forge-rifled barrels shows that patterns emanating from inside the tube can be seen outside.



- Paul




I always tought that came from the twisting of the tube as it is pushed thru the rotohammer.

--------------------
Andreas

"Yeas it kicks like a mule he said, but always remember that its much worse standing on the other end"


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DarylS
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Re: OSR, Double Damage and Barnes' Response [Re: 450_366]
      #152284 - 31/01/10 04:10 AM

You are correct, Andreas. The barrel turns in the hammer mill, or the barrel is stationary and the hammer mill rotates up the barrel. I believe there have been both types. Either way, this is how the rotational grooves are impressed on the outside of the hammerforged barrel. They do not come form the inside. Styre chose not to remove all of the marks at the breech end as they are rather sexy to some people. They merely smoothed, reduced and polished them.

Paul - extra stress on the barrel as the bullet goes up the barrel will increase pressure that is readable on strain gauges placed along the tube.

The transducer method of presssure recording actually shows the rise from zero pressure to peak over time and distance, as well as the pressure curve from chamber to muzzle. This is displayed on a graph. A single transducer should show comparative pressures for different bullets launched at the same velocity. This system has been used since the 70's by some outfits.

--------------------
Daryl


"a gun without hammers is like a Spaniel without ears" King George V


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