Barrel Wall Thickness

[paul shields]

In perusing descriptions of Parkers for sale on the web, I've noticed that a few dealers list barrel wall thickness while most do not. Is it risky to buy one without this data? Is there any "rule of thumb" for minimum thickness, like for 12 or 20 ga barrels? Thanks for any advice!

[David Dwyer]

Paul
I feel it is absolutely necessary to have a barrel wall thickness before you buy any Parker. On a 12 ga I use .025 as a minimum. Many a pitted barrel has been honed and that will let you to look for what else has been done to the gun
David

[Steve Huffman]

For what type of steel is the min .025 is this for damacus and fluid both as well as stub and twist I am wondering.

[David Dwyer]

Dam and fluid

[paul shields]

Would it be different for a 20 ga? I should have said before, that's my primary interest. Thanks

[Harry Collins]

Paul,

There is greater pressure as the gauges go from 12 to 16 to 20 etc. I would want a little more than .025 but could be mistaken.

Harry

[Dave Fuller]

I think I'd want to know who's doin' the measurin' and how... its a bit of a tricky business.

[Drew Hause]

The Field March 7, 1891 Vol 77:325
http://books.google.com/books?id=inQCAAAAYAAJ&pg=PA9-IA6&vq=Damascus&source=gbs_search_s&cad=0#PPA9-IA6,M1

http://pic20.picturetrail.com:80/VOL1373/6511424/17546456/365573248.jpg

UK Working Standards recomended minimum wall thickness measured 18" from the barrel breech from Double Gun Classics p. 56, Vol. 1, No. 4 Jan-Feb, 2006:
2 1/2" 12g- .028
2 3/4" 12g- .032
Re-proof recomended minimum- .024

The Hunter's Encyclopedia from the German proof house: minimal wall thickness at end of chamber, regardless of length, for 12, 16 & 20 gauge guns should be 2.3mm (.0906") for 'ordinary good steel' or 2.1mm (.0827") if a 'Special Steel' was used. For the 24 & 28 gauges, due to their higher pressures, 2.4mm (.0945") was recommended.
Minimal wall of .6mm (.0236") was recomended in the "forward third" of the barrel.

[Bruce Day]

So if you start with typical Parker wall thickness of say .032 for all gauges ( heavy waterfowl guns were thicker) and honing once often takes .008, then you have .024, and then a second hone to clean the bores because used gun buyers like shiny bores because it shows the gun was not used much, another .008, and you are at......


I'm aware of a 20ga Parker ruptured barrel in the forward 1/3rd, wall thickness .006, but those bores sure were shiny. No obstruction.

[Steve Huffman]

Bruce Is not .006 below the mwt. of .025 that some say is ok ?

[Jack Cronkhite]

Bruce: On that 20 ga, based on the .008 loss per honing, those barrels would have been honed at least 3 times to get down to .006 if starting at .030 if I got the math right. This leads to my continuing education questions.

Does honing serve a practical purpose verses a cosmetic purpose?
Does light pitting cause problems for continued shooting?
Hypothetically, does a single deep pit [let's say it leaves .020 at that spot] have the same potential for barrel destruction as the honing to remove it or would honing the entire barrel be far more problematic?
Finally, is there a means to fill a pit and leave the bwt alone, as opposed to remove steel to the depth of the pit thereby reducing bwt over the entire barrel length?

Drew: The barrel schematic shows no forcing cone. I'm wondering about bwt around the cone. Thoughts?

Thanks,
Jack

[Bruce Day]

Jack, here's my take on it. I know others have studied the issue also, and I am a big fan of the Bill Murphy philosophy of "don't mess with them".

1. No, except that unpitted bores are easier to clean. So just scrub more.

2. No

3. Don't think so. Would you rather have a small single isolated potentially weak spot or would you rather have the entire barrel length potentially weak?

4. Don't know, other than a full length liner, which is a drastic and expensive remedy.

[Drew Hause]

"Is there a means to fill a pit?"

I've discussed with a few TIG specialists, and no.

[Jack Cronkhite]

Drew: So we can rule out TIG welding. I have often wondered if some of the advanced epoxy resin systems might fill a pit without resorting to welding. Is there something inherently wrong with epoxy/steel combo that is made flush to the inside of the barrel?? Don't know, just asking.
Cheers,
Jack

[Robin Lewis]

The Field March 7, 1891 Vol 77:325
http://books.google.com/books?id=inQCAAAAYAAJ&pg=PA9-IA6&vq=Damascus&source=gbs_search_s&cad=0#PPA9-IA6,M1

http://pic20.picturetrail.com:80/VOL1373/6511424/17546456/365573248.jpg

UK Working Standards recomended minimum wall thickness measured 18" from the barrel breech from Double Gun Classics p. 56, Vol. 1, No. 4 Jan-Feb, 2006:
2 1/2" 12g- .028
2 3/4" 12g- .032
Re-proof recomended minimum- .024

The Hunter's Encyclopedia from the German proof house: minimal wall thickness at end of chamber, regardless of length, for 12, 16 & 20 gauge guns should be 2.3mm (.0906") for 'ordinary good steel' or 2.1mm (.0827") if a 'Special Steel' was used. For the 24 & 28 gauges, due to their higher pressures, 2.4mm (.0945") was recommended.
Minimal wall of .6mm (.0236") was recomended in the "forward third" of the barrel.

Thanks Drew, I incorporated this information and some of the other comments to improve this FAQ.

Thank all for your input, it helped too.

[Tom Carter]

Dr. Drew,

Please check your PM. Tom

[James T. Kucaba]

Thanks Drew, I incorporated this information and some of the other comments to improve this FAQ.

Thank all for your input, it helped too.

Robin ... What a great illustration ! ... I hope everyone prints several copies for future reference ... THANKS !

Jim Kucaba ... AriZOOna Cactus Patch ... Email: JimKucaba@aol.com

[Jim Williams]

Bruce,

Your example of taking .008 from the BWT for a first "honing" seems extreme. To remove this much metal, usually they would be reamed instead of honed, but that's just academic to this discussion. The point I want to make is that using your example of taking .008 from the BWT would mean adding .016 to the bore dia. So, a typical .730 bore would now be .746 after one reaming, and a second would make the bore a whopping .762.

I have found that reaming in steps of .005 over bore dia. often cleans up most pitting, and if not, another .005-over usually will. In the first case, you only take .0025 (two-and-a-half thousandths) off the BWT, and in the second, still only .005. If necessary, we could go up another .005 and now be .015 over original bore dia. (.745), yet after three reamings still not have taken off quite as much as your example of one reaming (.0075 vs. your .008). There is a reason bore reamers are typically sold in .005 increments. But you have to remember that reaming x-thousandths from the bore only removes 1/2x-thousandths from the BWT.

All that said, I agree with you and Bill. Really not much reason to fool with it in the first place, and I usually don't.

Jim

[Bill Murphy]

I have a Parker that was pitted when I got it and it doesn't seem to be pitted now and I never did anything to it except scrub and shoot it for many years. I also bought a "ruined" A Grade Fox 16 gauge several years ago. After a very agressive scrubbing session, the barrels were as new. I think some "minor pitting" is really surface rust. It isn't rocket science to mic the inside of the bores and compare the measurement to the known standard. Some exceptions to the Parker standards were on the big side, but I think we know what is unreasonable and indicates a hone job.

[Jim Williams]

Bill,
Are you using your discarded sheets of old sandpaper to make shot-column wraps for your reloads? ;-)

[Bill Murphy]

That would be the easy way.

[Tom Brown]

Would anyone know what the wall thickness would or should be at the muzzle for say imp. cyl, mod, imp. mod, full on a 0 frame 20 gauge Parker? Thanks in advance. T.

[Austin W Hogan]

Adding the numbers on Dr Drew and Robin's sketches give a breech width of 1.205 inches. Two 1.205 diameter barrels would be 2.410 inches; a two frame is 2.375 across the standing breech and most Parker barrels look like sewer pipe when compared to an English gun.

Best, Austin

[Dean Romig]

and the chamber wall thickness of most Parker barrels look like sewer pipe when compared to an English gun.

Best, Austin

Sorry Austin - I thought your statement needed a little editing ;)

[Austin W Hogan]

I just took the micrometer to the chamber wall of a 1 1/2 frame DH which is a little under 7 pounds. It measured .190 inches. There must be a lot of lightening holes in those 6 and 6 1/2 pound English twelves if they have a .287 thickness. I think the diagram is in error; adding .080 for the difference in bore diameter and chamber diameter makes it a little closer, but not quite as thick.
A three frame ten is .245 at the breech.

Best, Austin

Added; Bill is correct, a flat or dovetail is cut to join the barrels at the breech removing about 1/8 inch from the breech width.
I just measured a three frame 12 ga barrel. The chamber wall is .265 inch thick. The barrels are stamped 5 12

[Bill Murphy]

Austin is right and the diagram is wrong, at least for a breechloader. No English bird gun has .238 chamber walls. A second thing to consider is that the barrel wall thickness at the chamber is not doubled at the inside in most double guns. Austin's .190 chamber wall dimension is way less than .380 between the chambers of a 1 1/2 frame Parker. The one I just measured is only about .308.

[Tom Brown]

Just to clarify things, what should the thickness of the choke wall be for imp. cyl, mod, imp. mod, or full on a 0 frame 20 gauge Parker? I measured the thickness of my choke walls except would like to know what other choke wall thicknesses measure. Thanks in advance. T.

[Austin W Hogan]

The thickness of the barrel depends primarily on the frame size with respect to gauge, and secondarily on length. The barrels were finished by longitudinal hand filing to fit a general set of outside diameter checks. The filing was generally done to balance the gun at the hinge, but it could be muzzle heavy or light if the customer ordered. The longitudinal hand filing produced barrels that were not necessarily concentric with the bore, and wall thickness can vary side to side or top to bottom. There is no standard thickness.
Some guns appear to have thick barrels because full choke barrel muzzles are .040 or more thicker than the bore.

Best, Austin

[Jean-Paul Lavalleye]

Following up on Drew Hause's above post regarding The Hunter's Encyclopedia from the German proof house, is there data of actual measurements, current or old, of Parker barrels minimal wall thickness at end of chamber, regardless of length, for 12, 16, 20 & 28 gauge guns?

I currently own three Parkers on which I've made this measurement using Hosford and Co. barrel wall thickness gauge. The chamber minimum wall thickness data for these is as follows:

1.) BH 12b. on a no. 1 frame, R ≥ 0.088, L ≥ 0.094 (Damascus barrels)
2.) GH 20b. on an 0 fame, R ≥ 0.100, L ≥ 0.092 (Damascus barrels)
3.) DHE 28b. on an 0 frame, R ≥ 0.084, L ≥ 0.076 (Titanic steel barrels).

All of these have been shot for many many years (not by me) and measure up well in terms of min wall thickness and bore diameters. Kirk Merrington tells me that, in his experience, Parkers and other American guns tend to have wall thickness at end of chamber that are considerably less than found on English or German guns (in the 0.080"-ish range). Yet this does not seem to be problematic. The Sherman Bell articles of a few years, in the Double Gun J., regarding the strength of Damascus barrels would seem to support this conclusion.

Is there data somewhere that would show how low you can safely go with these thicknesses (or how low Parker went when they were making these guns)? I am currently looking at a 16b. Parker on an 0 frame where that minimum thickness (for a 2.5" chamber) is 0.068" on one chamber and 0.071" on the other, with all other measurement being fine; bores at 0.667, min barrel wall thickness at 0.030." This gun has very obviously been shot quite a lot. Is it safe?

[Daryl Corona]

JP,
I looked at that 16b you are referring to on Sat. and without any way of measuring other than by my eye they looked just fine to me. Your measurements of the BWT seem to me to be quite acceptable and the bore diameter is well within specs. I would have no problems shooting it with low pressure handloads or RST loads. Have the barrels been blued? I did'nt examine them that closely but that is a sweet gun. I was really interested in the smallbore P grade with twist barrels.

Daryl

[Jean-Paul Lavalleye]

Here are some minimal chamber wall thickness, at forcing cone end of chamber, I've measured for shotguns either in proof (bore diameter in proof 9" from the breach) or (for a very few of those listed below) so deemed by Kirk Merrington. All also have min wall thicknesses of ≥ 0.020, preferably ≥ 0.025.

English:
James Purdey (1898) 12b., 2.5" chambers: ≥ 0.100.
James Woodward (1909) 12b., 2.5" chambers: ≥ 0.098
James Woodward (1909) 12b., 2.5" chambers: ≥ 0.103
Boss (1897-8) 12b., 2.5" chambers: ≥ 0.090
Westley Richards 12b., 2.5" chambers: ≥ 0.090
James MacNaughton (1895) 12b., 2.5" chambers: ≥ 0.095
Wm. Pape (1898) 12b., 2.75" chambers: ≥ 0.100
EM Reilly (1887-1904) 12b., 2.5" chambers: ≥ 0.091
Henri Egg (1870) 12b., 2.5" chambers: ≥ 0.108
WH Monks (1875-87) 12b., 2.5" chambers: ≥ 0.116
WC Scott (1905-6) 16b., 2.75" chambers: ≥ 0.105
Francotte (1938) 12b., 2 5/8" chambers: ≥ 0.098
Westley Richards (1905) 20b., 2.5" chambers: ≥ 0.098
WW Greener (1922) 20b., 2.75" chambers: ≥ 0.098

Belgian:
Francotte (1894-5) 12b., 2.5" chambers: ≥ 0.085
Francotte (1896) 12b., 2.5" chambers: ≥ 0.085
Francotte (1930) 20b., 2.5" chambers: ≥ 0.095

French:
Verney Carron (1950s) 12b., 2 5/8" chambers: ≥ 0.100

German:
Wilhelm Brenneke (1902) 12b., 2.5" chambers: ≥ 0.110

If we are concerned about shooting safe vintage guns, shouldn't we be concerned about the thickness of the metal where the chamber meets the forcing cone, where the pressure is higher than further down the barrel (where we look for ≥ 0.020") and how low (thin) can we go? Looking at the data above, is a 16b. with a chamber wall that is 0.076"-thick at the forcing cone OK (even though the barrel wall min thickness is 0.030") safe to shoot? The answer to this question seems to be "yes" as this Parker had clearly been shot quite a bit and still has factory specs. Is there actual data somewhere on this point?