just to add to what SCJ429 has posted the sine/stress wave moves forward and back along the barrel till it runs out of energy and dies out
apparently the wave can reach the muzzle and return to the chamber end up to 4-5 times before the bullet leaves the muzzle and the node will be best when the wave is at the chamber end of the barrel
this is all about finding a sweet spot node where your rifle shoots at its best for the recipe used not really about why?
"Yeah kind of is relevant...all things being equal - how would you explain a shot that hits an inch higher on the target but chrono speeds were exactly the same ?"
the answer l would guess would be the flyer was caused by inconsistent run out or a case that has a bend in it, the reason a lot of long range shooters index there cases, there is no such thing as a perfectly made case no matter what the brand
if you have a proven load and you get a flyer its not because of harmonics period, and dont we all hate them flyers

getting a 100 fps higher velocity has to be because of more pressure caused by more powder, smaller internal case volume, bullet seated deeper, do-nut forming, neck tension ect..
there are heaps of loads with very high ES that shoot extremely well at short range but they are no good after say 200
its the way l think about it anyway, l cant stand getting flyers, the more consistent your practices are the more consistent your results should be
