doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Barrel Measurements, your thoughts ?

I was looking at a drilling at the Southern last year 12x12 over 9.3. I asked if I could go measure it and test fire the shotgun barrels.
When I took the barrels off, the German proofs were 16 gauge 65mm. Someone had opened it to 12 gauge 2 3/4".
I did not test fire it and promptly returned it.

I have a 20ga Coswell and Harrison ca 1973. Proofed at .615. Both barrels are spot on .615. the left barrel drops to 19 thou about 6" from the muzzle. It was just made that way, best I can figure.

My barrel wall thickness gauge will be at the Southern along with my bore gauge. I usually leave them in the truck but will be happy to check out a gun. I have 4 rods, so can measure 10 to .410.

John Hosford covers some his travel expenses measuring barrels and selling bore gauges. I feel like I am supporting him by not openly measuring guns.

Joe in Charlotte

.1 would be the answer.

.1 in that area.

The point of this thread is a good one. Dealers who sell large numbers of guns are not uninformed about what and how to measure things as a rule. If I as a minor collector, can justify the cost of tools to measure guns completely and can learn how to use them correctly, then a dealer certainly can do so as well. And if they do know why would they not be willing to pass along all the information unless it hurts their cause to sell a gun.

We have no proof laws in this country to protect the consumer for guns that are in unsafe condition. A visual inspection is not adequate in this case. I suspect most dealers take one of two pathways. They choose to never know, so they can always resort to it is up to the seller to have the gun inspected before use in case of a problem or they know and do not want to share all the information with the buyer. You might still buy a gun with thinner barrels, but it would become a point of negotiation if you knew they are thin or you might just walk away completely. That $6,000 gun may be more like a $3,000 gun with thin barrels. It certainly will be a lot harder to sell to an informed buyer.

As a general rule I rate gun dealers (with some exceptions) just about one level above used car salesmen.

Looking at a Woodward offered by a UK dealer last week I was told by the dealer that both sets of barrels "are in proof". Upon inspection by a dealer I trust it turns out that one set of barrels is out of proof. The offering dealer, at various times, quoted the LOP at anything between 14-3/4" and 15-1/4". Pretty gun and maybe someone will buy it, but not me.

Some years ago I was asked by a friend to examine a couple of Fox guns that a friend of his had bought. Upon examination these guns both turned out to be 'composed' gun made of various odd parts with serial numbers erased and re-stamped.

British proofs are a great aid in buying, but they do not address wall thickness. I have a couple lightweight Brit doubles that have wall thicknesses as low as .022, but the guns are well within proof based on the internal diameters at 9" from the chamber at the time of proof, which can vary quite a bit. For instance a Brit 12b is nominally .729" but can vary from .710" to .740". Once you sort out all the various proofmarks and the period in which they were used they can tell you a lot about a gun.

Still, Caveat Emptor

Proof is only an internal measurement. Is it within .010 of what it passed proof at? The walls could have been .050 or .020. Wall thickness has nothing to do with proof. Guns have recently passed proof under .020, one I was told had a barrel at 015. I do not know where it was that thin. It could have been 2” from the chokes or at any other point. They do visually check before and after but they only measure internal before at 9”. If not bulges, rivelling or other visual defects occur and they stay on face with no action damage they pass. Now I am sure their visual inspection is 100tikes better than mine would be after thousands of examinations.

Passing proof is a snap shot and give only a little assurance of safety. But it does help you determine if a set of barrels have been honed to death. Nasty pits are hard to remove and require even metal removal from the entire inside area so as to not create a weak section on the barrel wall. If one side was .035 and the other side was .015 you can foresee a real issue. But in proof is one standard we like to know. Wall thickness is another.


What happens later is another matter. If you have a dent or bulge the barrels will suffer metal loss as that is corrected. If you have pitting, internal or external, that may require metal striking or honing to clean it up. That will also require metal to be removed and a thin area. When I see a gun at proof dimension of .720 that remains at .720 that has an area of wall thickness of .020 I pay close attention to location and to see if the entire barrel in that area reads the same or if it is localized. That .720 was measured at 9”not everywhere.

Size does matter. Location matters. Was it a dent lifted, then struck before refinish? Does it run the same from top rib to under rib? The gun remains in proof. A dent will be thin in one area and thicker near the ribs. An internal cleanups are more even in all directions. You home a perfect circle but strike a area down in one localized spot. Trust but measure and if it seems odd ask others or better yet just walk away. Odd often is a warning that you need to take heed of.

Its actually a real eye opener when you have Jon Hosford measure a set of barrels while you are watching and you see the dial move up and down as a set of barrels are measured. Many barrels have a small bit of ripple to them. Actually pretty easy to see with the right light in the right place while you are looking down those barrels at the right angle. As I mentioned I had Jon measure a set of barrels and it certainly seemed at some point in time a dent was raised and then the barrels cleaned up. That thin spot was pretty obvious with Jon's tool with Jon operating it. Reality was it probably wouldn't have caused a problem, but why take a chance. Life is way too short and there are plenty of other guns out there.

I'm not surprised. I know a few dealers who probably don't have the tools to properly measure a gun. That dosen't make them dishonest just lazy

zzzzzzzzzz....

I'd be interested in recommended bore measuring gauges. I'm not looking for the best of the best if it's particularly expensive. My needs are not that frequent. But I would like to have something to measure bores and chokes and chambers more precisely. A Skeets bore gauge seems to be unobtainium, though I have searches for it built into likely places that one might surface. Any other good ones? Or ones to avoid?

I do have a wall thickness gauge that I bought recently at an auction thanks to Phydoc's alert. It came with a partial set of bore diameter gauge pieces but nothing useable, unfortunately. So, a recommendation for a bore measuring gauge would be welcome.