Stress Relieving a Barrel After Contouring

Just to clarify and not to be argumentative, broaching is a cutting operation. I will freely admit that, at some level any metal working technique will require the application of a certain amount of force. Under normal circumstances, however, it can be considered insignificant. By far, most distortion during a cutting operation comes from the removal of internal stresses along with the material removed.
Plainly, stress relief done nearest to the final sizing/shaping will result in the most inert finished product. Likewise, stress relieving procedures which have been omitted at critical points in manufacture are likely to result in distortion which is not correctable with remedial treatment. So button rifled barrels MUST be stress relieved prior to turning. This because the button rifling process IS a metal forming and, therefor, stress inducing process. Distortion which is likely to occur during machining of an non-stress relieved barrel, will remain even if the piece is subsequently stress relieved. Likewise distortion resulting from heat treating will remain even if the piece is subsequently annealed. ( Actually, a small amount of the distortion may be removed by normalizing or stress relieving but it certainly will not be eliminated. I've been there. Often.)
It is probably worthwhile to mention that art h. is correct when he says that changing the shape of a piece always changes stress potential at some level. I don't think this is of any real consequence in the barrel turning/machining scenario however.
Machine a piece of tubing which has been formed by being drawn on a mandrel and you will witness some significant distortion. Stress relieve the piece prior to machining and you will not see any distortion.
Warpage which occurs during heat treating is warpage which occurs from the introduction of stress into the material. Unintentional changes which occur as you machine this piece are the result of stressed material being removed.
Stress relief subsequent to the machining operation is closing the door behind the escaping horse.
As I said previously, the inportant thing in this instance is that the MRC barrels are properly stress relieved after they are button rifled and show little tendency to warp. Regards, Bill
 
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