doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com How much is too much pitting?

My project becomes more challenging than I imagined or hoped. The good side is that it is a firsthand opportunity for me to learn. That is, with your knowledge and benevolence.
Unfortunately, the 16 ga Darne barrel that I would like to restore has some pitting both on inside and outside. Most of the pitting is right in front of the chamber and some at the muzzle. It does not seem to be very heavy or very deep, but I don't know.
From a safety standpoint, how much pitting would be too much to shoot (or not)the barrels. The barrels seem to be made of thick steel. They are stamped 17.0 (.669") on both for ID and they are .735 for OD at the thinniest point, 12" from the breech. That gives a difference of .066 or .033 for the wall thickness at the thinnest point.
Is this thickness enough to ream out some of the pitting?
Isn't the minimal barrel thickness somewhere around .030" enough for safety reasons?
The chamber is 2 1/2" and the barrels are nitro proofed with tripple proof, which I think stands for over 18,000 psi of pressure in French.
Of course, the easiest is to send the barrels to a specialist, but that would shorten my learning experience. I might end up doing just that so I don't lose a finger or...
As always, I much appreciate your help.

Sliver
Since your gun is triple proofed, you might try just extending the forcing cones (according to the British proof houses that won't put a gun out of proof). With long forcing cones you'll accomplish several things:
1. You'll get rid of some of the pitting
2. You'll be able to shoot 2-3/4" shells without ruining the hull
3. Some believe long forcing cones give you better patterns.
I've done that in several of my guns and have been very pleased with the results.
It's worth discussing with your gunsmith at least.
Steve

The bad thing about a pitted barrel is it's almost impossible to properly clean.

Rockdoc,

You are right, I would have to explore a few options. Mike Orlen might be able to backbore the barrels and get rid of the pitting or just lenghten the cones. I don't think that lenghtening the cones alows for shooting longer shells. One does not lenghten the chamber but only the cones...
Did you notice an improvement in the pattern with the cone lenghtening?

jOe, does the pitting stop with the oiling of the gun?

It sounds like you're making two assumptions, the barrels haven't been honed before, and that the bores are exactly concentric with the O.D.'s of the barrels. One or both assumptions may be incorrect. The only way to accurately determine wall thickness is to get the walls measured with a guage designed for that purpose. Personally I'd send the barrels away to get objective data and then make an action plan based on what I found out. Silvers

HJ is right about rough barrels being hard to clean. I have a 16 that I've run a hone through to smooth the pits out, but are still rough. To clean the things takes forever. You just have to live with it.

Silvers,

I am assuming both possibilities as long as we talk in general terms. I agree that a gunsmith should take a look at the barrels, measure them, then I might know what options I have. It seems that even the measurement of the barrel thickness may be a task not easy to accomplish.

eeb,

The cleaning does not concern me as much as the shooting of the barrels. It is a "junk" gun. I don't have high expectations for a perfectly restored gun, but rather a shooter that I can safely enjoy in the pursue of a grouse or two.

Some of my old hammer doubles have lots of pitting. I did do some measurement to determine average wall thicknesses and some sort-of measurements on the deepest pitts. From a shooter's perspective, these barrels shoot quite nice patterns. Actually, the most pitted set of barrels shoots some of the most even but tight patterns of any of my doubles.

What I do with 16s is use a 12 gauge Foster slug to actually slug the bores at 10 cm increments and then measure OD at those same distances. Gives a good average, apparent wall thickness, on assumption that bores and exteriors are concentric. So far, I have found that ALL of my nice old shooters have been reamed but still have apparent average wall thickness that are 0,035 inches or more. These are nearly all guns that have been heavily used, so, no surprise they have been reamed at least once.

I have quit worrying about pitting making them hard to clean. I do sort of "condition" pitted barrels with fine emery paper, which seems to remove jagged edges on the pitting. Then, I just clean normally, with oooo steel wool on brass brush, and then spray RemOil down the barrels and let them stand vertically for an hour or two. Then wipe with wads of kitchen paper towel, which removes the many flecks of powder fouling that RemOils floats to surface.

These guns have been fired many hundreds of rounds since I got them, one maybe over one thousand. No problems with low pressure target loads or many fewer low pressure hunting loads. I shoot few SAMMI spec load in these guns, usually only to get hulls for reloading.

Niklas

Possibly sending the barrels to Mike Orlen would be worthwhile to get his evaluation as to the damage and possible remedies? He does specialize in barrels.

Thank you, all.