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Joined: Mar 2005
Posts: 709
Sidelock
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OP
Sidelock
Joined: Mar 2005
Posts: 709 |
Maybe I don't understand the problem, but in lieu of an expensive device to measure barrel wall thickness,(some of which are worthless) why not just measure the inside diameter of the barrel then use a simple micrometer to measure the outside diameter. Half of the difference between the two is barrel wall thickness.
I don't want to but the knock on Midway, but I think some of their videos should be taken with a grain of salt.
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Joined: Dec 2001
Posts: 6,273 Likes: 205
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 6,273 Likes: 205 |
No guarantee of bore and outside wall concentricity is why each wall must be measured multiple places.
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Joined: Jan 2006
Posts: 9,428 Likes: 315
Sidelock
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Sidelock
Joined: Jan 2006
Posts: 9,428 Likes: 315 |
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Joined: Mar 2005
Posts: 709
Sidelock
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OP
Sidelock
Joined: Mar 2005
Posts: 709 |
Yes, multiple measurements is a must, but it just as easily done with a mic.
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Joined: Jan 2002
Posts: 866
Sidelock
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Sidelock
Joined: Jan 2002
Posts: 866 |
pooch, your suggestion can be used as a rough guide,HOWEVER, concentricity is one problem, the other is that an outside micrometer,because of the rib, cannot measure the outside wall accurately,and this is often the area that suffers most from dents etc. and thin spots are found.
Better to keep your mouth shut and be thought stupid,than open it and confirm.
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Joined: Jul 2010
Posts: 707
Sidelock
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Sidelock
Joined: Jul 2010
Posts: 707 |
It is not uncommon to find a gun out of concentricity by .015".
Your .032" minimum wall thickness may be only .017"!
A true wall gauge is the only way, anything else is deeply flawed with meaningless results.
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Joined: Mar 2005
Posts: 709
Sidelock
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OP
Sidelock
Joined: Mar 2005
Posts: 709 |
Barrel wall measurement under the rib cannot with any device I am familiar with. A barrel bored off center by .015 would most likely fail initial proof. A Spanish gun may be the exception.
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Joined: Dec 2001
Posts: 3,964 Likes: 89
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 3,964 Likes: 89 |
I am currently polishing a barrel whose wall thickness varies from .025to .040 at the same point. The manner in which it was struck at the factory or repaired later on can make a huge difference in thickness that cannot be discovered without a wall thickness gauge.
When an old man dies a library burns to the ground. (Old African proverb)
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Joined: Dec 2001
Posts: 3,964 Likes: 89
Sidelock
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Sidelock
Joined: Dec 2001
Posts: 3,964 Likes: 89 |
Barrel wall measurement under the rib cannot with any device I am familiar with. A barrel bored off center by .015 would most likely fail initial proof. A Spanish gun may be the exception. You are right, Pooch. However, barrels were frequently heavily struck after they had been joined. Therefore it is most likely that the barrel under the rib is thicker than any other part.
When an old man dies a library burns to the ground. (Old African proverb)
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Joined: Mar 2005
Posts: 709
Sidelock
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OP
Sidelock
Joined: Mar 2005
Posts: 709 |
You need access to the inside and outside of a barrel to measure its thickness, unless you have a rather complex X ray instrument that can take slices. The barrel thickness inside the rib presents the same problem to the barrel wall thickness gauge as it does to the simple micrometer.
A .015 off center would show up when you are micing the outside, if were only at one point. To be .015 off and not picked up by the outside mic, the barrel has to be bored .015 off center the length of the barrel. Since we are usually investigating guns that nearly 100 years old it difficult for me to imagine a barrel wall initially being .020 and not have failed by now.
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