Shooting: Its Appliances; Practice; and PurposeJames Dalziel Dougall 1875
http://books.google.com/books?id=-ToCAAAAQAAJ&pg=PA25&dq=damascus+barrels&lr=#PPA24,M1
There are various kinds of flaws in barrels, such as "cracks," "sand-holes," and what are technically termed "
grays." The first two are comparatively rare, but the last is the great annoyance of the barrel-forger and gun- maker; and, in fact, may be said to exist more or less in all barrels. They are those little specks in the iron which may be seen more readily after a gun has been used, from the rust showing more upon them than upon the smoother surface. In themselves, unless very numerous, "grays" lead to no insecurity in the barrels, and are not real flaws ; but the freer barrels can be made from them the better, as, unless when kept clean and well-oiled, they may in course of a long time deteriorate the barrel. As a rule they cannot be detected while the work is in progress, and only make their appearance on the barrels being browned. Conversely, strange as it may appear, most frequently they become less apparent in course of time, and on the barrels requiring to be browned a second time, disappear altogether. The reason why the first browning causes them to appear is that the infinitesimal quantity of oil they contain neutralizes the chemicals, and the mark is then for the first time made visible. The reason why they eventually disappear is their extreme shallowness. The very finest of barrels may therefore, and often have been, rashly condemned by sportsmen for harmless spots which no foresight could prevent. Were they actual flaws, they would appear during the process of filing.
The "
sand-hole" is a thorough flaw; and if the barrel stand the proof at all when it exists of any size, still it cannot be quite safe, as the hole will often run in a tortuous direction for a considerable length under the surface, being, as its name imports, full of fine sand, or probably of the powder used as a flux to promote complete adhesion in welding the barrel, which has adhered to the iron, and been closed upon in the act of forging. The Damascus barrels, in contradistinction to "laminated steel," I have always found in my experience the most free from "sand- holes." Indeed of late years I have not known an instance of this flaw, through using Damascus barrels in preference to all others. Many an annoying instance I had in the days when "laminated steel" was puffed up, and when, after a gun was nearly finished, a "sand-hole" would be discovered, into which I could insert a piece of fine flattened wire and pass it half-way round the barrel between the laminae.
The "
crack" is the worst of all flaws. This is a separation of the fibres of the iron from overstraining of the twist; and consequently every discharge of the gun must, by the expansion of the metal, more or less widen the crack, until it run right round the barrel. The same "solution of continuity" may also exist from imperfect forging, and the same result takes place. The author has repeatedly taken old double barrels asunder, with a crack in one of them so lengthened through time that the barrel was nearly separated into two parts. When this crack runs round the barrel the danger of bursting is exceedingly remote; but should it have a longitudinal direction, or if there be two near to each other, the danger is much increased, and, sooner or later, the barrel will give way. The longitudinal crack almost never occurs; and all the varieties of Damascus barrels are the most free from this kind of flaw. A hole right through a barrel would be much more safe than any kind of crack; and, in point of fact, many barrels are safely used for years with a small hole right through them. A crack may at once be detected by suspending the barrels, and striking them with a piece of wood, when, if faulty, they will not emit the clear, ringing sound they otherwise do.
The inside should be as bright as a mirror, and free from flaws. Slight marks or rings, left by the boring bit, can hardly be avoided, and may be found in the best barrels; but there should be no hole (pit) likely to retain dirt or damp of any kind, which can corrode the iron.Since the introduction of breech-loaders these slight marks form a frequent subject of remark. The tube, being open, is glanced through, and the presence of such a mark is detected, whereas with a muzzle-loader this might never have occurred. Timid sportsmen fancy there is danger where none exists. In the first place, writing of course of these unavoidable marks only, no good gunsmith would permit any barrel with a real flaw to leave his hands. His final loss would be greater than his first. But besides that, in the tentative process of making a gun shoot well, he is bound by necessity to leave the barrel as it is the moment he has developed its shooting powers to a recognized standard. Hence he is debarred from polishing out any mark or discoloration for the mere sake of appearances. In breech-loaders the master-gunsmith enjoys the same opportunities to detect flaws as the sportsman, who may rest assured that the confidence put in the good faith and judgment of the former is not misplaced. The same minute marks existed in muzzle-loaders, and were known to do so by all gun-makers and by most experienced sportsmen, yet no one thought of challenging them; they were taken as a matter of course. The facility of looking through the barrels of breech-loaders has caused these utterly harmless marks of boring to be considered something new and improper. The spots are infinitesimal in size or depth, and are only visible through contrast with the bright polish of the general tube. The barrel never deteriorates with time through their presence.
Good barrels will often, when subjected to the same circumstances which would burst an inferior article, bulge, or swell out, like a glass tube heated at one part and blown into. When the bulge is not very large it may be partly hammered down, but no barrel so treated can be called truly safe, until subjected to a fresh "proof."
Making the decision to use any firearm involves a calculated risk. None of us can answer Dr Bob's question; and apparently there is no commercial/scientific technique to assess pattern welded barrel integrity. Dr Bob can run an endoscope down the bore and get a lot better look than the rest of us
As said before, judging the quality of pattern welded barrels is based on the quality of the
gun. "Belgium Laminated Steel" (Twist) barrels on a JABC are not of the same quality as the barrels used on a high grade Lefever.
My concern is that deep pits will dissect into a weld and lead to barrel fracture. It took quite a bit for Sherman Bell to rupture poor condition barrels, and none 'exploded.'
To diminish the risk, one might have H.P. White Laboratory, Inc. in Maryland proof their barrel. I have no experience (
anyone here?) Per
Shooting Sportsman March/April 08' it ran $420.
www.hpwhite.com 410-838-6550
