doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Proper technique for a barrel wall thickness gauge

I bought a Manson Precision Wall Thickness Gauge (I'm not coughing up the $$$ for a Hosford) and I'm getting results that vary too much to be right...so I'm doing something wrong.



I'm sure there's a proper technique, and I'm not doing it that way.

Obviously I have to keep the ball on the end in contact with the inside of the barrel while attempting to keep the arm it is attached to parallel with the barrel wall...but I must be moving it around too much.

Dewey Vicknair has demonstrated just how little lateral pressure it takes to deflect the long round bars on this type of wall thickness gauge, causing inaccurate and inconsistent readings. Naturally, they cannot tell you anything about wall thickness under and between the barrel ribs. And the ball cannot reach down to the bottom of pitting to determine just how deep they really are. This subject has been discussed here numerous times in the past.

They are better than nothing in the hands of a skilled operator. Someone will be along shortly to say Dewey is wrong, but your experience proves otherwise.

Helpful thread
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=615160#Post615160

It is critical that there be no movement of the barrel during the process.

this is a great gauge...

it will give you any reading you want...

Geoff, you don't say how you are using your gauge, vertically or horizontally. The picture is maybe not clear, but to be accurate the bar with the ball needs about a quarter inch extension of the bar past the ball. It appears the gauge "feeler" does not touch the ball while in repose. Of course that cannot be the case, but that how it appears. If your gauge was made as I described, and was used horizontally , you can get perfect readings every time.

I became frustrated with this style gage and took the plunge and bought a Galazan gage made in the British pattern, I like it quite a bit more than the style shown above.

That gauge can certainly be used to relative and effective precision, and it is sure better than ignorance and other guesses. Damn the naysayers, full speed ahead. AND you damn sure shouldn't take grief for asking questions...
So to answer your question... it does take some time and effort to get a good feel for it. I believe it definitely should be worked vertically. I assume most of the fine details are in the thread posted above... I did not go look, but I read several threads here through out the years. In my experience, it does require a firm but fluid touch/ motion and a gentle up and down and back and forth. That should at least present repeatable numbers and a general feel for the general geography of the barrel. I always check top, bottom and outside of each barrel, and then worked larger degrees when thinnest areas or areas of concern showed. In getting the feel, I would personally find it tought measure at exactly one spot..... if that makes sense? As in my motion or the set up may not fit exaclty every inch or some other target.... but I could get a good read on a spot right near an inch -being more focused on the feel and the measurement than hitting an exact spot.

Years ago I made one that I believe Miller (RIP) posted. His hung from the ceiling on a hook. The only problem with it was that you needed someone to write the readings down, or else you had to remove the barrels , write down your findings, and then start over where you left off. I got tired of that and was talking to a friend who had a Galazan thickness gauge. This one had 3 different bars, one for 10-12 ga, 1 for 16 ga. The hardest part was milling a tapered slot where the spring and lever part was flush with the rod. I don't have a milling machine and had to set the bar/s up on an angle and use an XY table on my drill press.I can read from the breech 16 inches. The breech end fits on a tapered cone that fits into the chamber and is adjustable with a thumb screw for different lengths along the barrel. In reading from the muzzle end, if the chokes are too tight I cannot go over the rod which is 5/8" (.625) and half the diameter of the ball .0625. Together that is .6875. So I can read at least 16 inches and really beyond that, most pressures I shoot under 7500 psi, so I'm not worried too much.
I can redo the readings, and they come out within a .00l or less, plus I can write everything down because the barrels are centered on the cone and the spring lever is holding them in place at that point.
Keith is right, nothing within our means can measure between the top and bottom ribs.

https://imgur.com/CRSvRu6

https://imgur.com/67vgW5I

https://imgur.com/wD9V0un

The last photo shows a reading of .057, 8 inches from the breech.

Thanks for pointing that out - the photo is inaccurate...I'm not sure why they use it on their website.

When you set the gauge up, you drop the feeler to the ball and set the zero there.

Thanks - have no time for the naysayers and people who criticize folks who ask questions. Let them sit in their little bubbles of self involvement and self pleasure...

As you said, this device is fine for what I need, I just need to use it to get the best results I can.


Thanks. I like the idea of using it vertically....and I really appreciate the walk though on how to use it.