doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Barrel Wall Thickness Gauge

As you can see above I have pulled one of the drawers of my workbench open and placed a piece of plywood upon the drawer and positioned the wall thickness gauge on the plywood. This allows me to look down onto the gauge for maximum visibility. If you look to the right of the plywood you will see the white drawer pulls of the other several drawers

Dustin; Thank you for posting the above photo.

Stephen Howell

All the gauges I have seen have solid bars. Wouldn't a hollow bar be stiffer than a solid? Or perhaps a hollow bar with external flutes as in modern rifles? Just asking because I have always been told that hollow tubes are stiffer than solid bars and resist bending moments better.

Shotgunlover,

I think you have missed out the words “weight for weight”.

Well?

The stiffness of the uprights of a shotgun barrel wall thickness gauge of course is an issue that is of concern to the users of such a gauge. In England I examined the shotgun barrel wall thickness gauges in various gunmakers shops during the several times I lived and worked there. Two items stand out in my mind in viewing these gauges in those shops: (1) all of the gauges I saw were built by the craftsmen in these shops---not "store bought"; and (2) all of these gauges had uprights shorter than what we see made here in North America. Some gauges I have seen in use by British trained gunmakers have the uprights no longer than maybe 10 inches, resulting in stiffness of these uprights be of little concern.

Shotgun gunmakers, barrel makers and gunsmiths of significant experience know where the thin wall area of a shotgun barrel is going to be within maybe 95% certainty---6 to 9 inches from the muzzle near the ribs.

Take a look at the photo above of the shotgun wall thickness gauge in use and see that this thin area of the barrel is within the range I just quoted as well as where it is. The range of the wall thickness of this barrel was .024''-.029".

Regards;
Stephen Howell

I would think 3/8" carbide rod would fix the flex problem. A bit pricey though.
A quick google search yielded 299.00 for a 24" piece. Im sure 18" would be cheaper.

Make a heavy base, mount a 1" square x approx 18" long steel post to mount the indicator. Silver solder a .437 ball on the 18" carbide rod and mount it on the base.
Should be pretty stiff!!

I like Stephen's gage and his views on length of rods and others on the flex that there might be. I made this one using a 6"x6'x 1/2" steel plate, 5/8" rod for 10-12 gauge and a 1/2" rod for 16-20 gauge. i can measure a 32" barrel end for end providing the choke area is more than .694 (includes rod diameter and .067 ball protrusion on 5/8" rod. On the back side of the rods is a brass rod that is spring loaded and tapered to fit in the tapered slot in the rod/s. I mounted a level that lets me get horizontal and vertical when a barrel is mounted, also the brass cone at the bottom centers the barrel on the rod.
As far as flex goes, my concerns about 9" from the muzzle doesn't bother me because at this distance the pressure has dropped significantly. I also mounted a ruler next to the rods that lets me repeatedly re-do my measurements. I can take the barrels off and put them back on the get maybe .001-002 variation.




I use this on my shotguns and like stated is repeatable. I rotate barrels from top rib to bottom rib taking the lowest readings and do so every 4 inches permitting. I also reload my own and only shoot low pressure (8000 psi and under) and low velocity (1200 fps and under.)

Another picture showing how the spring-loaded brass rod is attached.



In the other photos showing the ruler the reading of .057 is 8" from the breech