Quoted:
Quoted: I've heard that if a barrel is turned down, SOMETIMES it spoils the accuracy of the barrel, particularly if the machining was done too aggresssivelky (too large a cut) or the barrel got too hot.
CJ
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I see it's the re-turning of the barrel not the profile. If not done right this would be a problem.
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Actually, cmjohnson has a good point. What sometimes happens is that turning the outside of a finished (rifled) barrel will often release internal stresses left over from the rifling process.
The method of rifling the barrel has a lot to do with this. Cut rifled barrels (both single point cut and broached) are virtually inmune to this problem because of the near zero stress placed on the barrel walls by the rifling method.
Button rifling is a little worse, which is why they are rifled after being turned to the final profile. In most cases, stress relieving the barrel before altering its original profile will prevent the distortion.
Hammer forging, which so many here adore, is BY FAR the worst method of making a barrel because of the large amount of radial stresses placed on the steel by the forge hammers. Even after being stress relieved after forging, HF barrels will usually walk when being turned after finishing. A competent barrelmaker can straighten one out, but it should be no surprise that no riflemaker interested in accuracy will use a hammer forged barrel.