Originally Posted by Bart B
Please, folks, get in touch with a mechanical engineer who's knowledge and skills are what you trust.
A rifle barreled action is exactly like a guitar string when plucked with a pick or finger; it vibrates at the same note (frequency) each time. Only the loudness (how much it swings back and forth making sound waves) changes directly with how hard or soft it's plucked.
All this stuff about "harmonics" is grossly misunderstood by 99.99% of all rifle shooters. Once the rifle's built, its barrel whip frequency and harmonics thereof don't change......ever!!!! Shoot a round or smack it with a ball peen hammer; it vibrates the same for each.
Fair enough. I can't say I dissagree with these statements except that I don't think I need to seek the advice of another engineer or that 99.99% of all shooters grossly misunderstand harmonics and that I believe frequency intensity can be different when different varibles are interjected. In other words, heavier or lighter bullets with a bigger or smaller internal explosion will cause more or less intensity as well as different wave node locations. The point I am trying to make is that the bullet still has to exit the barrel at a given point in the 'frequency' for best results. Also, you can't compare a guitar string to a rifle barrel. One has a fixed boundary and the other has an free boundary.
When I refer to 'harmonics' on this site, I am referring to the frequency of barrel whip you describe. There will always be a dead or neutral point(s) (AKA: 'wave nodes') on the barrel as well as a maximum amplitude. Max amplitude occurs between the wave nodes. Exit the bullet at max amplitude ('anti node') and the results suck. Exit the bullet when the barrel is in line with the 'wave nodes' and life is good.
I think it is you who said that you had experienced high hits at 1K with lower velocities and hit lower with bullets going faster. As you stated, this was due to 'barrel whip' I understand this principal. The bullet is exiting the muzzle while various points of the barrel are in the 'anti node' point in the frequency. The anti node is the point where the amplitude of the sine wave is at its maximum. That said, if you exit the bullet at the right time for that frequency the effects of high hits for lower velocities and vice versa is eliminated. The bullet needs to exit when the whole barrel is on the same sheet of music with the wave nodes for the best possible results. If you can find that sweet spot, it is typically referred to as the 'harmonic node'.
You can illustrate the point I am trying to make by holding an arrow (this works best with no insert or tip) horizontally with one hand by the nock and tapping the arrow in the middle of the shaft. You will feel the vibrations with the hand that holds the arrow. As you tap closer to the open end of the shaft (free boundary) the frequency becomes less intense. When you get to a certain spot, there is a 'dead' spot or 'node'. All you feel is the tap of your finger and NO vibrations (AKA: 'frequency'). Then, when you pass this dead spot itself, you feel the harmonics again. There is also a dead spot between the middle of the shaft and your fingers holding the arrow. When you interject an insert and tip, this dead spot or node moves with different weights on the head. The heavier the weight on the end of the arrow, the closer to the end the dead spot will be. Target archers typically want their arrow rest on or very near this dead spot (AKA: 'wave node') for the most forgiving launch. These dead spots are 'wave' nodes. There is a point during the frequency wave where the whole arrow shaft is straight and in line with these wave nodes. In other words, there is a time during the frequency when the arrow is straight. If you can visualize that, then you can see why you want a bullet to exit the muzzle when the barrel frequency is at 0 amplitude.
I am sorry if I did not use the right 'verbiage' in a previous post to lead you to think I need to consult an engineer.
Are you an engineer?