Barrel Analysis

[Drew Hause]

The Modern Sportsman's Gun and Rifle: Including Game and Wildfowl Guns, Sporting and Match Rifles, and Revolvers
John Henry Walsh (Editor of The Field) 1882
http://books.google.com/books?id=OLwUAAAAYAAJ
“CONSTRUCTION OF THE GUN”
http://books.google.com/books?id=OLw...cad=0#PPA83,M1
THE BARRELS
Whatever may be the kind of gun about to be made, the first thing done is to forge the tube or tubes containing the charge. Formerly they were all made of plain iron, but for the last hundred years the barrels of all best guns have been constructed either of strips or twisted iron coiled spirally round a mandril, and welded together by heat, or of steel. At present the selection is from three kinds, viz., first, Damascus; second, laminated steel; and third, plain steel.
The chief difficulty in the present day is to obtain iron of sufficiently good quality to mix with the steel, whether for Damascus or laminated barrels. Formerly horseshoe stub nails were alone thought good enough; but of late years these have fallen off in quality, and are also insufficient for the supply of the increased demand for shot guns since the passing of the present game law. These stubs, generally mixed together with other "scraps," were welded together and forged into bars; but in the present day new iron is alone used, selecting the best quality in the market, and refining it by melting and puddling, after which it is submitted to the tilt hammer, by which its fibres are condensed and drawn out.

[Gunner]

Richard, I have questions regarding "Aston Twist Parker barrels." I am not familiar "Aston Twist" How are such Parker barrels marked on the top rib and on the barrel flats if they are marked? Is this twist distinctive in appearance from other twist barrels? Do the surviving Parker records distinctly reference "Aston Twist" and have any letters documented same?
Thank-you for any information you can provide.
Erick

[Drew Hause]

An update
http://www.doublegunshop.com/forums/...=357105&page=8

[Eldon Goddard]

The results seem to me to be the same that Zircon posted and I discussed with him. Drew glad to see some one putting in the hard work.

[Drew Hause]

Eldon: One important difference is that Bell's blown up barrels were subjected to sequentially greater pressures until failure, and DID show low cycle fatigue. The blow out being investigated now was a single over-pressure event, and low cycle fatigue was NOT seen. This is important in that it has been claimed that all Damascus eventually fails from internal rusting and weld failure (NOT seen) and low cycle fatigue.

[Eldon Goddard]

Yes that is true. I was thinking about the failure at weld lines. But I should have read more closely before saying that.

[Drew Hause]

Some here have no doubt been following the thread on DoubleGun, but here is the short version of the Metallographic Analysis from METL, and my conclusions:

I believe the burst was caused by an obstruction, likely the shot wad from the previous shell, lodged in and just past the forcing cone, caused by a light powder drop in reloading and incomplete ignition from the very low temperature. There may have been a pre-existing bulge also.

1. Did the barrel fail related to low cycle fatigue? NO

The fracture surface exhibited a mixture of ductile overload (plastic deformation with both tensile overload and shear) and transgranular cleavage indicating a ductal failure mode with rapid failure. The cleavage failure appeared to form preferentially in the iron component. No evidence of fatigue failure was observed; there were no striations on the fracture surface.

2. Did the barrel fracture at a ribband edge weld, between iron and steel rod welds, or within a rod? NO

The fracture did not appear to trace along the ribband (spiral) welds. Some cracking was seen along the individual bands within the crolle pattern, but this was not always the case.

3. Did the barrel burst related to interlaminar rust, inclusions, voids, or embrittlement? NO

No evidence of embrittlement was observed. There were a large number of inclusions but there was no apparent fracture jumping from one inclusion to another. The composition of the inclusions was predominantly silicon, phosphorus, and sulfur ie. slag.
No voids or interlaminar rust were observed.

While the microstructure was banded, and the bands had different grain size, inclusion content, and inclusion form (globular in the iron and linear in the steel)... “the overall material appeared to be a single piece of metal...(without)...microstructural defects.”

Chemical composition was similar to AISI 1005 low alloy steel. The low range of tensile strength is 40,000 psi, but may be heat treated to much higher numbers.


METL now has 17 barrel segments (14 pattern welded and 3 fluid steel) for tensile strength testing, and the Hunter Arms Armor steel section will also have composition analysis so we'll KNOW what at least one c. 1900 tube was made of, and can compare it to the barrels in Dave's study.