It's all stuff that's been discussed here and on other forums over the years, but nice to see it in one place.
Rimfire5 said:
IMO, the shooter set-up variation and trigger discipline causes most of the variation.
That's because most shooters are not top-tier. When you get to top-tier marksmen, it often is no longer true, and all sorts of mechanical limitations of the equipment can be detected by them. In one of the books mentioned in the video, Harold Vaughn's
Rifle Accuracy Facts, he induces dispersion with intentionally poor cartridge concentricity in loads fired from a special 6 PPC rifle that is built into a machine rest that has had all the deflecting recoil moments determined and eliminated, and firing that in his 100-yard sewer pipe range, shoots the same load into one hole consistently when the cartridges are concentric. A.A. Abatiello did something analogous with human shooters '60s by getting top-tier marksmen with match Springfields to shoot samples from 47 lot numbers of National Match ammunition that were first sorted by concentricity and was able to make a calculation of the effect based on the physics of the bullet's orbital off-center CG that matched with the added dispersion in the groups the shooters were turning in with that ammo.
lugerstew said:
…do they always use Hornady components?
If you use their online 4 DOF calculator, you will find some Berger, Lapua, Sierra, and Warner Tool, and a couple of Nosler bullets have been included in their list of those they have measured drag functions for with their Doppler radar setup. I think you can expect them to want to know how their product compares to others, so they will be testing other things for that information and to decide what is worth trying to improve on in their own line. What you can't expect is that they will disclose when someone else's stuff does better. In the case of brass, so to speak, you can bet they have price points they don't want to exceed and, thus, will have limits on what they will spend to make brass as precisely as some others do. However, machining, in general, keeps getting more precise, so there may come a time when you can't really tell much difference between brands, accuracy-wise.