There is a lot wrong with your thinking that powder charge is #1. You might need to go weigh some of your bullets. You will find a big variation in brands, as in grains. I shoot a lot of 45 70. I now cast because of variations in weight. One manufacturer 405 grain weighed between 391 gr. to 416 gr. Also brass manufacturers have big variations in volume and thickness of brass. For example: the load I use in 308 Federal brass will not work Lapua brass. Lapua Brass has way less volume then Federal Brass. To the point of crushing and compacting powder. Which will in fact create more pressure to the point it could be unsafe. But my 308 rounds with Varget, federal brass, federal match primers, SD 3.4 (which can be improved on) has a 5 inch group at 1000 (with very little wind). I suck when winds are blowing. Toprudder can go into it even more. His name is MR.TEST.
I guess I did not qualify my comments or assumptions. My BE coach tests and shoots different bullets based on his conversations with other Camp Perry champions or winners.
I only shoot 9mm and 45. My comments were based on consistent loading of know components. In talking to him, I have been doing what he does or following the advice of competitive shooters in their blogs or forums.
I use Starline brass for both calibers. I use Blazer for “everyday” 9mm shooting. Variable or variation is now controlled
I shoot tested (BE) bullets or some recommendations from others. I have bought “a lot” of supposedly another members excess and it was a known brand, type, size, etc. Either he got a bad shipment or it was mixed. Two separate runs...flat base with shiny finish and dull with indentation on base. They are now sorted. So, by experimenting with one particular brand, type, model number or whatever .... another variable removed.
Sizing die set up so that deprimed cases drop freely in and out of Williams gauges. That eliminates a variable that Dillon was not picky about.
Belling or flaring is a function of case length. I know that my Starline cases will bell or flare 0.010-0.012. Same setup and Blazers, which are longer, will flare 0.013-0.015. But when you seat and crimp same bullet in each, the COAL is the same and the dummy loads easily pass the Wilson gauge.
I HAVE looked at weights for a small sample of certain bullets. I don’t need an Excel spreadsheet to look at the % variation or the weights to know they are at least an order of magnitude less that the powder charge variation.
so....back to my original assumptions....I think they are correct for my shooting and evaluation. Given that, then from a consistency standpoint, you control the largest variable to maximize results.
now....do I point the barrel up, down or forward and bang or tap the frame so that the powder level, for each round, is consistent. Nope....but some folks do and publish the chrono results and SD....as well as minimizing the COAL...
NOT THERE YET...
Appreciate your comments, but I think mine are correct knowing the circumstances and assumptions...