Eccentric wall thickness

[John Havard]

I'm broken hearted over having to return a very nice DHE that I bought over the internet because of its barrels. It was from an estate sale, had almost 90% original case color, vibrant D4 damascus barrels, eye-catching wood, the whole schnizzle. It was in extraordinary condition and was something that I had been wanting for quite a while.

Using my Hosford wall thickness gauge I checked the barrel walls and found that the top of the right barrel paralleling the top rib for about 6" had a thickness of only .018". Imagining a cross section taken through the barrel and viewed from the breech end would place the thin barrel section between 1 and 2 o'clock. At 3 o'clock the wall was at .024" and by 4 o'clock on the cross section it was at .032". This section of thin wall ran from 16" to 10" from the muzzles. The left barrel had nothing under .024".

Both bore diameters were consistently .732" so perhaps at some point they had been polished - it's hard to say. The chambers had been lengthened to 2 3/4" which was a major turnoff and might suggest polishing. However, removing .003" from a true .729" in the course of polishing the interior of the bore wouldn't cause the eccentricity I measured.

Has anyone else ever run into this? And I'll be posting a "want to buy" note in that forum.

[Mike Shepherd]

I have two Parkers with original bores and .019" wall thickness just behind the chokes, both in the right barrel. One a Damascus DH and one a Titanic Steel DH. They are eccentric as is the referenced gun but not by as much.

Best,

Mike

[Russ Jackson]

John ,I have a PH 20 Ga. for sale on our site now and also on GB ,that has basically the same scenario as you are mentioning ,but the thin wall is only about 4 " in length as Mike says directly behind the Choke 19 Thou.. I have carried the gun for years ,and have had no problems ,I shoot RST low pressure through it ? My bores do not appear to be honed or polished ,but as far as selling this gun I have had little interest in the gun and I imagine this is the concern ,mine is in the Left barrel ! Russ

[John Havard]

Well, the location of this thin stretch of barrel starts just in front of the fore end where the leading hand would be placed. Admittedly on top of the tube and not directly against the hand. Small consolation if it ever decided to let go none the less. I just didn't feel right about trying to use the tubes with that deficiency.

I also wanted to share this info because it might make some folks aware of the need to inspect barrel wall thickness very carefully and all around the circumference of the tube. A cursory check only along the side or bottom of this particular tube would have offered assurance of more than adequate wall thickness. Only when I rotated the barrel and checked close to the rib did I find the thin area.

Previously I would have expected eccentric wall thickness to have been on the side of the tube where it was easiest to strike. Instead it was on top and near the rib. A word to the wise for folks like me who are still learning!

[Mark Ouellette]

John,

The thinnest part of the barrels are often found adjacent to the ribs. I've read that this was do to striking. The good news is that after about 16" from the breech the pressures are pretty low. The bad aspect of this is that thicknesses of under .020" are very succeptable to dents.

Mark

[John Havard]

Yep Mark, .018" is about the same thickness as four sheets of bond paper. Not very thick and easy to dent!

[Russ Jackson]

Just to note ,I measured mine also with my " New Hosford Gauge " Every Dam. or Twist gun ,I have ever sold ,I was ask about barrel wall thickness and wanted to know myself ,The gun I am speaking of ,I was very confident the barrel walls were plenty heavy and was very suprised to find this small area with 19 Thou. thickness , the rest of the barrel thickness was excellent !

[Jack Cronkhite]

From the discussion thus far, it appears that a number of good guns have this eccentricity. If it was due to striking, then it is factory. If it was due to a poor job of honing, it is post manufacture. It would be interesting to measure up a lot of Parkers being shot to see if that is consistent enough theme to suggest it all happened at Meriden. Very interesting findings.
Cheers,
Jack

[Jack Cronkhite]

Okay, the suspense got to me. I have a GHE Damascus that has also been nitro-proofed and hunted extensively by its previous guardian and for a few trips last year by me. I could not come up with any area along the length of either barrel with BWT less than .030". She's a vg condition shooter and a keeper :)

Any eccentricity likely resides between this shooters ears http://parkerguns.org/forums/picture.php?albumid=160&pictureid=1964



and not in these barrels

Cheers
Jack
http://parkerguns.org/forums/picture.php?albumid=160&pictureid=1764

[John Havard]

Hi Jack,

I believe the problem lies in the tubes from the factory and not from honing. Assuming the tubes on this old gun left the factory with .729" bores and given the fact that both miked out at .732", and assuming that .003" was removed in honing, that means that the barrels were VERY eccentric when they left Meriden. The drastic change in wall thickness over such a short portion of the barrel's circumference must be due to striking the exterior of the barrels. Unless I'm missing something?

Beautiful old GHE by the way.

[Jack Cronkhite]

Thanks, the GHE is a fine gun and fits me well. When I miss, it's just my fault.

I think when honing a cylinder, the depth of cut (reduction in BWT) would be .0015" of metal around the inside circumference to achieve .003" increase of inside diameter from .729 to .732

Never done it, but that makes sense to me. I stand to be corrected by the experienced.

Cheers,
Jack

http://parkerguns.org/forums/picture.php?albumid=160&pictureid=1766

[John Havard]

Jack, indeed you are correct I'd think. In either case it suggests that the gross amount of eccentricity I found in the returned DHE was the result of work done in Meriden originally.