Put your mind at ease, Pete. The front sight band and sight base are integral parts of the barrel, machined from the barrel stock (but you already knew that and just wanted to stir up some fun <img border="0" title="" alt="[Wink]" src="wink.gif" /> ). While the major portion of the barrel is machined by "turning", the barrel band and sight base are formed by a process called "broaching" where the cutter moves parallel to the bore axis, as opposed to perpendicular, as the barrel is rotated.
(Would the real machinists please step in and correct me if I am displaying my ignorance!
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