Barrel Engineering Drawings

[Eldon Goddard]

A couple of days ago there was a drawing with dimensions of a barrel on the random picture of the day. Where can I get hold of that picture again. Does anyone have engineering drawings for a 12 gauge barrel that parker made. I would need the barrel wall thickness along the entire barrel. Planing on doing some engineering work on this subject while I still have access to expensive programs. If I could do some tests on the materials (fluid steel/damascus) I could settle this whole debate on strength, but that would be impossible without two sets of barrels to sacrifice, so that is out the door as I would not intentionally destroy two sets of barrels. Unless I can find some one who has already done work and has mechanical properties on both materials, but I highly doudbt I will ever find high strain rate dependent properties for damascus steel.

[Dean Romig]

You may want to discuss this topic with Dave Suponski. He has done some research on the subject.

[Bruce Day]

The Parker Story ( TPS) contains an entire chapter on barrels, which you may want to consult. Within 12 guages, barrel dimensions differed by frame size, intended use, and user choice. Thus, No. 2 frame 12ga's had barrels that weighed anywhere from 3 lbs 10 oz to 6lbs. I have seen unaltered 12 ga's with wall thicknesses ranging from .028 to .050 at mid length. A typical 12ga No. 2 barrel set will weigh 3lbs 14oz and have mid length wall thickness of .034 to .038, with chamber thickness of about .120, or to match frame bolster width.

We have had various people over the years attempt to quantify the elastic and rupture strengths of the many different fluid steels and composite steels used by Parker, all to no publicly disclosed result. One fellow thought he would use NDI radiographic testing on damascus barrels to identify lines of weakness. Not unexpectedly, the radiographs showed nothing but a mass of lines from which no conclusions could be drawn.

At least two others have acquired barrels or barrel segments and commenced some sort of studies, but nothing has come of those, nothing was published or disclosed and the individuals have apparently lost interest or have been drawn off to other pursuits. Several people believed that those investigators were serious about their work and were active in finding barrels for the investigators , but so far as I know the investigators are no longer active and the barrels vanished.

The only published experiments so far have been the Sherman Bell tests reported in The Double Gun Journal. Those were for strength of composite barrels and have been discussed repeatedly here and I'm sure elsewhere if there are other internet gun sites.

[Kevin McCormack]

The H.P. White ballistics testing laboratory in Bel Air, MD should have some information on the subject.

[Eldon Goddard]

Thank for the information guys. I understand why there has not been much research as it requires quite alot of equipment and not to mention time, but I will try to get some work done on it while working on my thesis. I have also been looking into spread of shotgun pellets interestingly since they are supersonic it appears that the front pellets slow down more rapidly(a sphere is about the worst shape for supersonic flight) then the back and collide with each other after leaving the wad.

[Bruce Day]

Any relation to a certain Dr Goddard from Kansas?

You have hit upon the ill effect of long shot strings in small bores. The best patterns result from moderate speeds, short shot columns and large bores.

[Eldon Goddard]

No I do not think so but my family came from around there. Distant relative maybe?

[Kevin McCormack]

Did any of them wear red shoes?

[Bruce Day]

That is certainly a distinguished surname, as Dr Robert Goddard was the father of modern rocket propulsion.

There is a Goddard Kansas just west of Wichita. For Kevin, no I have not seen men wearing red shoes there, women yes, but not men. Since its summer, the custom for the fashion conscious is more white shoes and matching belt. Isn't that true everywhere?

[Drew Hause]

This was posted by ‘Zircon’ in 2007. Unfortunately, the testing effort apparently ended thereafter.

http://www.familyfriendsfirearms.com...p/t-55364.html
January 2007

I am doing a failure analysis of a pair of Parker barrels - one set damascus, and the other set homogenous Vulcan “fluid steel”. These barrels were used in the study by Sherman Bell and Tom Armbrust, published in Double Gun Journal (see above). They subjected each barrel to increasingly heavier loads and they both failed at about 30,000 psi. Modern ammo gets up perhaps to 12,000 psi. Most folks that shoot these old gals use shells loaded to the 7,500 psi range.

During the failure analysis I noticed that the fracture length for the Vulcan barrels was substantially longer than for the damascus barrels. A close examination of the fracture surface showed progressive, low cycle fatigue marks on the damascus barrel. The crack advanced slightly with each increasingly higher pressured load. On the Vulcan barrels, both sides failed by a brittle fracture mechanism. By this, I mean the barrels let go in one fell swoop. Even though both sets of barrels failed at 30,000 psi, the behavior of the damascus barrels was superior to the Vulcan barrels, owing to the fact that the Vulcan barrels failed in a brittle fracture mode. A ductile fracture trumps a brittle fracture every time.

One of the (myths) with damascus is that it will fail at the welds where the original rods were forge-welded together. When I looked at this particular set of damascus barrels using a metallographically prepared sample, and up to 1,000X optical magnification, I saw NO EVIDENCE of weld joint failure, slag in the weld joints, porosity in the weld joints, etc. I have about 30 old barrels in this study, homogenous, damascus, and twist included. I am a practicing metallurgist who holds an M.S. degree, and am qualified to state the observations of barrel integrity made in this posting.


On the two old Parker barrels, there is a screw hole that comes up from the bottom and pins the extractors in place. Both barrels failed at that hole, because it takes a (segment) out of the side of the chamber and is the thinnest portion of the chambered area.

The damascus barrel let go by a mechanism known as low cycle fatigue. Each succeeding round had higher and higher pressure. After several rounds, a crack started at the extractor screw hole. Each successive round caused the crack to open up just a bit further, until finally the overpressure could not be contained and the (barrel) failed in a ductile fashion. Ductile failures in steel look like a taffy pull at about 1500 to 3000X magnification using scanning electron microscopy. There is a cup and cone appearance with a lot of micro-voids present. This appearance is a dead-set giveaway to a ductile fracture.

The "fluid steel" barrel failed by brittle rupture. The fracture surface is more or less smooth, but has some "rivulets" in it that point back towards the initiation point, which again was the screw hole. The fracture surface was about 3X as long as for the damascus barrels. In other words, the same 30,000 psi final internal load created a lot more fracture surface in the homogenous barrel than in the damascus barrel. This indicates that, for an equivalent-length fracture, it took less energy to open up the homogeneous barrel than for the damascus barrel. The words in the Sherman Bell article were that the Vulcan barrel failed much more abruptly and (violently) than the damascus barrel.

So the verbal description of the failures during firing and the visual observations of the fracture surfaces are in accord with each other. Both barrels ripped lengthwise for some distance and then the rupture terminated in a circumferential crack. In the case of the damascus barrels the crack spiraled around with the weld pattern, but it was not on a weld, rather it was on one of the in-between areas. After the damascus pattern is formed by wrapping rods together and forging them into a strip (the "skelp") which is wrapped around a mandrel, spiral paper-tube fashion, and is forge welded together. These spiral welds remained tight and the parent metal is what failed. This may seem pretty amazing, but in many, many instances the actual steel welded structure is stronger than parent metal.

Many microphotographs, chemical analysis of the steel, etc. (will) make up the (anticipated) article. I'll also be looking at several other barrel ruptures and measuring the strength of the various barrel steels in the "hoop" direction as the barrel will always fail in hoop tension with a lengthwise crack. Any internally pressurized cylinder has 2X the force in the hoop direction as in the longitudinal (axial) dimension, so it's no wonder why barrels all seem to blow out with lengthwise cracks.