doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Measuring barrel wall thickness

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.

No guarantee of bore and outside wall concentricity is why each wall must be measured multiple places.

Relevant and informative thread here
http://parkerguns.org/forums/showthread.php?t=7889

Yes, multiple measurements is a must, but it just as easily done with a mic.

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.

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.

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.

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.

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.

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.