After a while we can probably agree on the idea that the linear math says one kernel of powder doesn't tip over an otherwise tuned load, and it would typically not show in a test that was designed to intentionally bias charges up or down by a kernel or two in reality either.
A POI node, and a velocity statistic are sometimes going to overlap well enough to stay several tenths of a grain wide, and sometimes they don't. If the POI node is decent, and we have a good ES/SD, then we usually have good performance out at distance. Without needing to pick a specific caliber or cartridge, the typical observation is that you would generally want those velocity stats to have an ES under 30 or they create too much vertical.
When you don't watch a CM real close, the ES in batches can easily create enough error in charge that we are not discussing a kernel or two, but more than two tenths. That sucks up your safety margin for keeping large batches in the center of that tuning node. Keeping a CM error down below 0.2 can and has been done, but it takes discipline and focus, way more focus than rejecting over or under throws on the FX120i.
That said, one of the concepts we don't hear often enough is the one about measurement uncertainty. Unlike some of the other comments about tests where folks did side-by-side runs with their CM and their FX120i, mine does show a difference. That means when enough rounds were loaded in several sessions, the CM uncertainty was high enough to cause some vertical dispersion when the sample sizes were large enough to have that statistic show up.
The Autothrow/trickler doesn't hold to a kernel, but the CM doesn't hold to 0.1 grains either. The point for me was that the AT/FX120i was about 3X better than the CM in terms of charge error ES and also faster when I ran it with two cups while running against Chargmaster.
It is one of those things in life where Better-Faster-Cheaper is a trade where we can often get two out of three, but it is a rare day when you get all three. The AT/FX120i isn't cheap when compared to the CM, but it is cheap when compared to the only practical alternative which is the Prometheus. However, the post wasn't meant to be a comparison of the scales.
The thread was meant to answer does a kernel make a difference. In reality it doesn't, but the question is usually not one of a kernel or two either. In the real world, we are not all BR shooters. Some of us want to load for multi-day trips. When you sit down to load and you are faced with a table covered with hundreds of hungry rounds waiting to be fed their charge, it isn't going to be to a kernel or two, but you still want to try and keep that error to a minimum. When you are not trying to hold to a kernel or two, you find yourself going over 0.2 grains in a session as a result unless you are going to exercise discipline and way more focus. For less effort, you can be within a few kernels.
