re: A rule of thumb on changing point of impact on fixed sighted guns

HMM,

quote:

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A nonconcentric bore was thought to provide more accuracy and batter harmonics.

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I'm not familiar w/ the concept of a non-concentric bore. I need to read up on that. Having said that, there a large number of things that contribute to gun accuracy. May just be internet lore, but supposedly it was happenstance that lead to Browning's development of the "BOSS." Supposedly the gunsmiths at Browning who worked on guns sent back to the factory found out that a large number of them became more accurate by bobbing off a small amount of the barrel at the muzzle. They thought that bobbing the barrel altered the barrel harmonics and helped the accuracy of many guns. The BOSS was developed so the shooter could adjust the barrel harmonics w/ repeatability.

Your most recent graph shows a good representation of the barrel (bore axis) and scope (line of sight) and how the two work together to produce mid-range trajectory. For many years I found the concept of mid-range trajectory very confusing.