Some of you are likely still following this thread
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=357105&page=1

I believe we're going to end up with a cascade of options for non-destructive testing of vintage barrels; fluid steel or pattern welded, starting with external and internal (via a digital bore scope) visual examination then measurement of wall thickness.

The problem with pin and micrometer wall thickness gauges is when pits are present. It is very difficult to position the pin exactly in the bottom of visually identified pits, and impossible if the pits are on the medial wall.

I hope to have the results of radiography on a second barrel tomorrow. This is a negative x-ray image of the first, which enhances the defects in the barrel wall, and may also be useful for measuring wall thickness



Dr Bob asked this question about 2 years ago, and received good advice on the thread and by PM.
The arguments seem to be:
Pro-honing
1. You can't know what's happening at the bottom of a pit, or how deep that pit might be
2. I've had some pretty ratty looking barrels cleaned up by EXPERT honing of as little as .0015", leaving plenty of wall thickness
3. If a barrel is going to be rendered unsafe by EXPERT honing, it's probably unsafe as is
4. The Birmingham Proof House requires honing before accepting a barrel for re-proof. They must have a good reason. Possibly Mike, Steve or Vic could inquire.

Against honing:
1. A barrel is not made stronger by removing metal
2. INEXPERT honing has probably ruined more barrels that anything else

My position is that 'don't look, don't measure, don't tell' is not appropriate. AND if a barrel blows, and a bystander is injured by the shrapnel, you ARE responsible. The personal injury lawyer is going to ask you to share the steps you took to provide some assurance that the barrel was safe, esp. since 'everyone knows Damascus barrels are dangerous.'

Please share your thoughts and opinions.

Drew, Is it then logical, that if one cannot know the depth of a pit that honing to the point where the pit disappears and measuring the wall thickness at that point would be the only way to really know what the true minimum wall thickness is? If the honing results in barrel walls that are too thin, it was unsafe to begin with?
How dangerous is a pinpoint pit compared to honing the entire barrel to the minimum thickness represented by the pit?

Then again I may ask how many angels fit in a pit.

Thanks brother. Yes, that is my position but I could certainly be confused this Lord's day morning
It probably depends ALOT on the location of the pit; I am MUCH more concerned about pits in the first 18 inches after which the pressure is less than 1200 psi with about any reasonable load.

I don't know if there's an answer to this although it pleases me that our clergyman professes confusion of a restless and searching heart!

Augustine of Hippo
"You have made us for yourself, O Lord, and our hearts are restless until they rest in you."

Quite a few Biblical references to 'the pit' also, but I'll stifle myself

Vintage shotgun barrels are not always concentric. Further, striking is usually more close to the top and bottom ribs. Only after a thorough examination using an accurate barrel wall thickness gage can one make any determination of if honing would be acceptable.

Observation using a bore scope is the first step. These scopes are available for less than $50.

I use my Hosford barrel wall thickness gage to make estimations of the thickness of pitting. Adding a couple thousands to the minimum thickness at the pit can provide a fair estimate. Once one has an idea of the minimum wall thickness under the pit the distance of the pit from the breech must be considered. How much will pressure be at that point?

If the above sounds like a lot with too many variables, it is. No wonder the British proof houses hone first!

I like to smooth out the edges of pitting with ball hones. Then the depth of the pitting can be more easily measured.

Hone or not? It is certainly a case by case basis.

I was hoping your x-ray results would prove a definitive method of determining the safety of these barrels, because in my opinion none of the other methods can really do it. You have a seam in the barrel wall, and all the looking and measuring in the world on both ends of that seam cannot see what is inside. That is why x-ray examination of seam welds on pressure vessels is necessary.

Huummmm- quite a few, sayeth thou, oh Drewbie-Meister. I can only think of three offhand- Them being all Yee Olde Testament gruppen- Genesis 37:20, Numbers 16:30 and Psalms 28:1-- what others am I missing, oh great Rabbi? Myself, I much prefer E. A. Poe's "The Pit and the Pendulum" with my drachma resting on the side of the pendulum of course- but WTF, what does a Mick Green Irish mackerel-snapper know about the Old Testament anyway? righto- Now to the main issue here- there are pits, dents, bulges and deformations in many sets of double gun barrels--honing or reaming is NOT a job for the average gunsmythe--and I concur with the other dude here who mentioned the sad fact that possibly more sets of barrels have been ruined by amateurs with set of hones and little knowledge of proper machinig practices- same numbnuts who open up full choked barrels witha reamer in the muzzle, and no piloted reamer from the breech forward to the muzzle area--

I'd tend to agree with DrBob's reasoning. I think a problem with honing is it seems more for appearance purposes rather than safety at times. Maybe, concentrating on the first six or eight inches of the inner barrel would be practical when looking for defects.

There seems to be an assumption that a pit caused the example failure, many on the original topic attributed the failure to some obstruction. I suspect the measure/scope advise doesn't hurt. Maybe jot down the numbers and recheck now and then for peace of mind on the guns that cause that little voice to speak up.

I think there may be some situation where a barrel fails slowly and measurable changes may show. If good practices are used, there might be plenty of hand load recipes on the lower pressure end to choose from. I don't think it's an option to just hang some of these guns up on a wall without giving them a decent chance.

Its not only old guns that have bores that are not concentric with the outside of the barrel. When I was doing gunsmithing in the 80's and 90's, one of the services I provided was the installation of screw in chokes. The process involved reaming the muzzle of the barrel to cylinder, then reaming with a special piloted reamer, then tapping with a special piloted tap. Sometimes the customer would want the barrel shortened at the same time, which removed the need for the first reaming. In many cases, when a Remington 870 or 1100 barrel was cut, the bore was visibly off center with respect to the outside of the barrel. When that was the case, the choke was also going to be visibly off center, so I always saved the cut off piece of barrel to show the customer that it wasn't something I had done. It is really no problem to keep the bore concentric when reaming with a hand adjustable reamer from the muzzle- it just takes more time. I don't know of any adjustable piloted reamers, so to ream from the breach end, you need an expensive assortment of reamers in each bore diameter, but if you have such reamers, the job is much quicker because you only have to make one pass. With an adjustable reamer from the muzzle, many passes, removing not more than 0.001" per pass, are required. Even so, I could ream a full choke barrel to cylinder, and install the choke in less than an hour of work.

Tom;
I agree with what you are saying here but with one "Important" Caveat.By taking those fine cuts as you describe the reamer will follow the existing choke on a Conical/parallel choke.
On a Taper choke as found on Lefevers as well as several other brands of classical doubles there is no parallel section for the reamer to follow. The reamer will in fact follow any angle it happens to be inserted at up to the angle of the choke wall itself. The alignment is entirely dependant upon the first few passes after which it will follow the parallel section established, which is entirely dependant upon how accurate one can "EyeBall" the reamers alignment to the bore inside which cannot be seen.

I have worked as a machinist and if you wanted to make a hole larger but be within specifications as to hole placement, you had to made a pilot to the size of the existing hole and attach it to the new counterbore to keep it to specification.
In reaming a barrel the principal would be the same, providing the bore was the same past the area you wanted to ream. A pilot would be made a thousandth smaller than bore and attached to the reamer/s. Not a hard thing to do.

I agree with Tom that newer barrels are not concentric either, somewhat better but not 100%.
Also the wall thickness near both ribs seem to be a few thousandths heavier on the ones I have measured.

When sending a gun for re-proof, it has to pass two inspections. The first 'view' is when the proof master looks at the barrel, and determines that it is fit for proof. that means it must be free from dents, pits, bulges or rivvels, it will also fail if it off-face, if a rib is loose or the loop is loose, or the lumps are loose.

Having ascertained that the gun is fit for proof, the gun is fired with a proof charge in each barrel. After this, it is inspected again to see if anything has changed - i.e if it now shows any rivvels, bulges, loose parts or deviation, or comes off face.

If it passes this inspection, it goes through the same process again.

If it goes out as it went in, it will be stamped with new proof marks.

So, if you want to submit a gun for proof, you need to have it prepared for proof. That means re-jointing very tight and cleaning up the barrels inside and out.

If you are not submitting it for proof - you have to take a punt. You will take the gun closer to being out of proof with every thou you lap out.

Sometimes, I clean up barrels a bit, sometimes I try to get all the pits out, sometimes I leave them alone.

Sorry that was not a very helpful instruction!

Drew and et al,
Here are two points that further complicate the mater.

If the pits are not removed inside the barrel, then the rusting can continue. When they are on the outside, bead or aluminum oxide blasting can remove the rust so it cannot continue.

If the pit can be stopped from further deterioration, it is probably safer to leave it from an engineering standpoint.

(I am a structural Engineer).

If a tension member has holes in it say for bolts, we size a tension member based on both the nominal gross area times an allowable working stress and the net area times the ultimate tensile stress. This is because the stress can flow around openings locally and still not fail.

I don't know if this helps, but IMHO, I think removing the pits is probably the best idea to stop the rusting as long as there is ample barrel thickness left. .... Or maybe using a non-etching rust remover like evapo-rust would work, if you can keep the pits clean.

Jerry