While installing some water lines to some pecan trees this morning, I thought of something that might readily demonstrate M25's excellent 'diving board' analogy from one of his earlier posts regarding barrel harmonics.
Take a piece of 3/4" PVC pipe and hold it in the middle and shake it. Then drop a marble or anything that will roll down it into one end, while still shaking the pipe. There are no guarantees where the object will go when it exits the pipe.
It's a very exaggerated example, but still shows what barrel flex will do.
Stiffen the pipe, or remove as much flex as possible, and you can control where the object goes a little better.
Same thing with rifle barrel harmonics.
The rubber dampeners remove some of the excess vibration.
Accuracy kinda boils down to timing, in a way, though. You are basically timing when the bullet leaves the barrel, during the vibration cycle of the barrel. Thinner barrels flex and 'whip' more than thicker more rigid barrels, but all barrels flex to some degree. I've seen benchrest barrels that were 2" in diameter to try to remove flex, just to shoot a 6mm bullet. But a 2" barrel ain't real handy in the deer woods.
Bottom line, remove as much vibration (harmonics) and as many other variables as possible and then work up the load (or test factory ammo) to find the round that is most consistent at leaving the barrel at the same time in the cycle of movement. Also bearing in mind that the load itself will have an effect on the vibration cycle, but you have to start somewhere.
This has been posted several times........Watch at about the 00:27 mark.
http://www.youtube.com/watch?v=s5pVya7eask