Well, it makes sense that seating depth, and to a lesser degree charge weight, would affect the timing of the bullet relative to ignition and exit of the barrel. The imagined Indiana Jones whip action is, of course, hugely exaggerated and a bit funny. Harmonics, I am convinced, actually exists, as that is what makes a bell ring. Setting off a small explosion inside good quality steel is bound to be similar to striking the barrel with a hammer, specially when the bullet is ejected from the cartridge and strikes the lands.
There is just a very small effect that likely results in a difference of likely less than half an moa (as a guess lol)
I have been experimenting with software that can, ostensibly, predict the needed timing provided all the inputs are appropriate. No conclusions yet, not enough shooting time invested.
Anyways, I find the whole harmonic timing subject fascinating.
"Harmonics" in the pure definition of the word absolutely exist. Everything vibrates.
The question is, 1) does that matter and 2) if it does matter, can we actually exploit it?
There's a lot of stars that have to align for all this to work consistently:
- Barrels/rifles have to react/vibrate almost the exact same way every single shot
- Our reloading process has to be almost exactly the same every round
- The components we use (brass, bullets, powder, primer, etc) have to be close to the same from part to part
All of those things have to *all* be in place before we can even begin to tune/tame the harmonics.
Now we have to be able to test in such a way that we are able to have a high degree of confidence that the changes we are making to our ammo are actually changing something. Which is much, much harder to achieve than most anyone gives credit for. And you have to do it without burning your barrel out firing enough rounds. Which is also hard to do as you really need larger sample sizes.
Just those things above have to all be in agreement before you even start testing. And then you have to figure out a recipe combination that is able to take advantage of vibrations so small they can't be (according to proponents) seen on cameras recording an extremely high frame rate.
And, all of that has to happen in someone's garage or backyard in their spare time. It's a monumental feet when you actually consider what people are claiming they are able to do.
Most people aren't able to even produce data that is worthwhile. For example in the pics I'm attaching, there is the chrono numbers for 5 shots on 5 different charge weights of powder. Which is a very common method people use for load development. It seems fairly clear that two of those charge weights are better than the other.
However, all 5 of those charge weights have the exact same Standard Deviation over a 100 shot sample. The 5 shot velocities were chosen at random from each 100 shot string. So, in reality, all 5 charge weights perform the *exact* same. However, the "data" collected via a common load development method shows otherwise.
This means that we are now using incorrect data before we even move into seating depth, tuners, harmonics....etc, etc.