I have never had much interest in barrel wall gauges because I believe for the most part, but there exceptions for sure, that if the bores measure spot on or very close to factory bore diameter specs for a specific gauge, then I assume the barrel wall thickness is safe.

Bill

One might get away with this philosophy in regard to American built guns like the Parker, Fox, L. C. Smith, etc.

Their barrels generally run a bit "thick" to begin with. Thus a hone or two might not be dangerous.

However, do NOT count on this approach with British or European guns. Especially those from the 19th or 20th centuries. Their barrels were often turned to a thinner overall wall thickness/contour to begin with. Thus, a bore gauge might suggest "OK" after honing, but the actual wall thickness could well be below safe limits.

It is also important to know where a barrel might be thin. Anything odd within the first 18 inches is vital to know about.

To paraphrase Gen. Douglas MacArthur, "there is no substitute for wall thickness."

Nice of the Belgians to tell us exactly the bore and muzzle constriction, weight of the barrels at time of proof, and load (only 1897-1903) for which the gun was designed.

12g Manufacture Liegeoise likely proved with Mullerite for a service load of 2.70 grams = 41.67 grains = 3 Dr. Eq. (42 grains) "E.C." No. 1 or "Schultze" with 36 grams = 1 1/4 oz. shot.
Note bore 22 cm from breech was 18.2 mm = .716". After WWI bores were generally 18.4 = .724"; honed to .729" would only be a loss of .0025" of barrel wall IF perfectly concentric.
If originally .716" and honed to .730" would be loss of .007" barrel wall.

http://pic20.picturetrail.com:80/VOL.../411806716.jpg

[QUOTE=John Campbell;205811]One might get away with this philosophy in regard to American built guns like the Parker, Fox, L. C. Smith, etc.

Their barrels generally run a bit "thick" to begin with. Thus a hone or two might not be dangerous.

However, do NOT count on this approach with British or European guns. Especially those from the 19th or 20th centuries. Their barrels were often turned to a thinner overall wall thickness/contour to begin with. Thus, a bore gauge might suggest "OK" after honing, but the actual wall thickness could well be below safe limits.

It is also important to know where a barrel might be thin. Anything odd within the first 18 inches is vital to know about.

To paraphrase Gen. Douglas MacArthur, "there is no substitute for wall thickness."[/QUOTE

Good point to remember, but for me personally, I have never even looked at a British gun, let alone have any desire to own one.

Bill

This may work very much against you because bore diameters varied greatly from early lifter guns and even later.
.729" may be considered the standard for 12 gauge but I know guns which measure over .750" and have never been touched.
You may err on the side of caution, and pass on a lovely gun that measures .740", assuming it had been honed eleven thous, you will loose out.

I made my own and it works well
 

Mr. Anderson is being very trusting of "factory bore diameters", which may vary by about .030 from gun to gun. I personally don't care if gun buyers measure bore diameters and wall thickness, but I will continue to do it after 56 years of paying cash for double barrel shotguns. My equipment cost me about $300, has been working for decades, and has protected me through hundreds of thousands of dollars of potential mistakes. A selling dealer who tells you he doesn't own a bore gauge is a liar. He just won't let you see him using it.

thank you Mark, you made me laugh.

Patrick

Not necessarily, if I know the bore diameter of a certain era of manufacturing states a bore of .750, then my bore gauge will confirm this for me. I said that I do not have much use for a "wall thickness" gauge if I know the bore diameter of the manufacturer at differernt points in production history, such as the lifter gun you mentioned. If I am looking at an American 20 gauge shotgun, for example, and find the bore between .612 and say .618 or .619, and I know they don't vary by .030, I see no use in a wall gauge if no pitting exists. Besides, I wouldn't own pitted guns in the first place. And if I believe I am looking a special "back bored" barrel I can always measure the inside of the bore and outside barrel diameter to give me a general wall thickness. True, not as thorough and complete as a top end wall gauge, but close enough to assess the safety of the barrels. And my collecting is but a couple, few guns a year so my methods will prevail.

Bill

Why myself of course. I think I clearly volunteered to be the first "idiot" to sign up for MWT training at the Vegas show if offered. I do this knowing that if given a precision measuring device I will either break it, “uncalibrated it” or consistently get different results measuring the same subject multiple times. If others have this same aptitude with these types of tools and object to my classification of their skill set then I sincerely apologize.

I previously had a MWT gauge from Brownell’s and I followed the directions sent with the gauge and could not make the gauge work. I then turned to the internet for some "enhanced" instructions and found a variety of solutions to using the Brownell’s gauge. I settled on the following set of instructions to get the most accurate results;

1. Make sure you are facing due north so that you are magnetically aligned with the earth to decrease the variance of measurements.
2. Suspend barrels from a floor joist in your basement to decrease anomalies in measurements. Use a joist at least 6 feet from an external wall.
3. Make sure humidity in basement is less than 28.5%
4. Enlist two additional helpers to secure barrels for test
a. One helper to hold the barrels
b. One helper to hold the first helper in place
5. Measurer will lift right leg and point due north to also be magnetically aligned with barrels(ok, I made this one up)
6. Insert measuring device into barrels and drag along barrel wall remaining PRECISELY level to get the most accurate measurements.


When my wife came downstairs and found the barrels hanging from the joist and George holding the barrels and Bill holding George and me trying to work the PRECISION measuring device she just shook her head and said “why don’t you just measure the bore dumbass! ” So, I sold the Brownells gauge and have followed the experts advice every since. :)

Patrick