https://youtu.be/Eh06tRr4t-k?si=ZXXi1ac-IRIjzNtIHere, Eric admits that Barrel Harmonics (prior to bullet exiting the muzzle) is only a theory, and he says “the reason that it’s a theory is we see group sizes change, the bullet doesn’t always go to the same spot”.
However, isn’t it the case that there is an inherent dispersion from shot to shot, regardless of what we do. The Stastical analysis by Blackburn Defense, and the large sample size testing by Hornady’s Lab, AB Lab and others shows that the ES and SD of shot dispersion grows with sample size. Therefore the evidence of barrel harmonics is just shot dispersion.
I hadn’t realised that, to date, there is no empirical data supporting the existence of barrel harmonics. But there apparently isn’t, it’s just a theory to explain shot dispersion. But is it good reasoning to treat it as such.
Vertical and Horizontal dispersion will be effected by velocity out of the muzzle, wind, BC (which itself is a gross up of angle of attack, centre of gravity, centre of pressure, spin rate).
Ignoring wind which is purely external, we are left with the others. Logically, in what ways could the internal ballistics have on those factors? The rifle basically gives two things to a projectile, velocity and spin. The dynamics of pressure over time from ignition to exit from the muzzle will impact velocity, simply as the quantity of push it imposes in the projectile as it is moved from the case neck into and through the rifling. It could be measured in Newtons or KiloNewtons. No matter how accurate our powder measurement, the tiny heterogeneous differences in The powder itself, it’s positioning in the case temperature and pressure, primer ignition dynamics all will sum up to a change in the Newtons that are acting on the bullet at different times during the bullets trip down the barrel. Small differences in the brass will impact chamber pressure, it will sum with those mentioned previously. Then the manner in which each bullet engages the lands will introduce an amount of resistance or the pressure developed in the chamber and so the velocity of the projectile in the initial inch of the rifling. After that the resistance of the rifling will add a variable, each firing adds some material to the rifling (copper, carbon some lead from the primer compound). shot to shot there is variance in the resistance of the rifling.
Then the physical properties of the chamber, bolt and barrel will react to the ignition and pressure with small variance from different pressures generated.
Finally projectile to projectile weight and shape tolerances will impact its travel through the barrel.
All these things add up to different velocity and spin rate of the bullet shot to shot.
These are enough to explain shot dispersion together, even if we take the human marksmanship variable out of the equation. In accordance with Occam’s razor; we don’t need to introduce barrel harmonics in the absence of evidence for it. That which can be asserted without evidence can be dismissed without evidence.
The aim of reloading is to get to as close to a homogenous Newtons of force acting on the bullet from ignition to muzzle exit. The question is, what methods in reloading contribute to uniformity and can demonstrably get us closer to homogeneity.
I don’t doubt that a certain rifle will tend more toward homogeneity with a certain bullet and load. There’s going to be an ideal pressure scenario for a rifle and projectile. The best proxy for this homogeneity is velocity SD and ES. Group sizes are useless to us because their sample size is compromised by statistical variance from external and human factors. Muzzle velocity has less confounding factors.
Reloading is the G O. The munitions produced by people in this sport is superior to factory made by a good margin. The attention to detail and discipline of production is a great example that even in the modern world handmade wins.
If you can get that bullet to spit out at low SD and ES’s of velocity, it’s a thing. I don’t know how much Spin rate will be effected by the rate of acceleration along the barrel. I can imagine that 2 projectiles could come out of the muzzle at the same velocity but that the rate of acceleration from ignition to exit from the muzzle; so this might be a potential confounding factor. But I suspect if we’re getting a low SD low ES velocity this is a good proxy for low SD low ES spin rate.
Speed is king, just not necessarily faster being better. My guns got an ideal speed, trouble is finding it.
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