necessary to keep the outer surface concentric with the bore. The final straightening leaves the bore approximately straight (very few bores are absolutely straight) and the tension of the metal such that it stays straight under normal conditions.
Now, a cut only a few thousandths of an inch deep, taken from the outer surface of such barrel, may, and usually does release internal stresses in the metal, causing the barrel to spring back to its original crooked or curved state as it was before being straightened.
A very common mistake of the amateur is to center his barrel in the lathe, and turn it down to the size wanted, without thought of straightening. The fact is, he probably cannot ttll by looking at it whether it is straight or not. He finishes the job and stocks the barrel and action, only to find that it is shooting far—very far—from its previous sight adjustment. Probably it is necessary to shift the sights well off center to bring the group into the black. And— here's the worst of it—that cussed group moves up or down, /right or left, stringing its shots all over the paper, as the barrel becomes warm from firing.
How come? The barrel looks straight on the outside—and probably is. But were you to saw it in two at the right point, you would find that the wall was considerably thicker on one side than the other—the difference often being quite plain to the eye, without any measurements. What has happened is that the very first cut taken from the outside sprung the barrel slightly, or else released stresses which permitted it to spring itself. Subsequent cuts, either lighter or heavier, sprung it some more—perhaps causing a compound bend; the light finishing cuts gradually turned the outside true and comparatively straight, while the bore remained crooked. Thus there are places where the wall is thicker on one side of the bore than the other, and this brings about a complicated state of affairs.
The crooked bore causes the barrel to shoot away from its normal sight adjustment; as the barrel becomes heated from firing, die expansion of the thicker wall being greater than that of the thin side, the barrel naturally bends itself in the direction of the thin walled side; and the hotter it gets the more it bends. There is no Temedy for this except straightening of the bore, and turning the barrel down smaller to make it concentric—straightening after each cut— and this is likely to reduce the size entirely too much.
The third result likely to be encountered, will be the increased "whip" of the thinner barrel, making it more susceptible to even the slightest variations of load; such a barrel is permanently erratic in its shooting, and there is nothing to be done for it. The best results that can be obtained from such a tube involve the use of only reduced loads, giving minimum vibration and whip—and the bullets should be selected by weighing and measuring, holding them within limits of 1/4 grain, and of .0005 inch diameter; and powder charges should be weighed, and held to 1/10 grain. Really the best thing
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