"How the bore runs on the ends of the barrel doesn't tell you what is happening between them. Every gun barrel made has a portion of the bore that is a little off center. Some more so than others. Your higher quality barrels are generally more concentric. I've seen barrels, with their bores so far off center that you would become disoriented watching them spin in a lathe, shoot remarkably well."
You just nailed it (in my view, anyway)
+1
GTC
