The best across the course shooters I know buy good brass, and then load them and shoot them. One bud set a couple of National Long Range championships did the same thing, and another, who won a couple, did the same. Buy good brass, load it and shoot it. Now these guys are sling shooters, maybe the F class guys are seeing something.
I am of the opinion that this practice is one of those advertising induced behaviors that we run across all the time in our society. I recommend reading books on Mass Marketing to understand just how Corporate advertising bureaus change our behaviors and create demand, where demand did not previously exist. (I recently read this one:
Satisfaction Guaranteed, The making of the American Mass Market https://www.amazon.com/Satisfaction-Guaranteed-Making-American-Market/dp/1588341461) I will need to see more than 5 shot, 10 shot, over even 20 shot groups, before I will accept that there is an accuracy difference between brass in which the flash holes were trimmed, and brass in which it was not trimmed.
And this is something I would like to know, just what is the difference? If the difference was MOA, we would all agree it makes a difference, because the error is so large. If it was a half MOA, I think we would all agree because a large body of shooters would see it, even though a larger body of shooters would not. But the number of shooters who would see would be large enough that we would reach a consensus that the affect was real. But, if groups sizes vary by less than a hundredth of an MOA, is there anyone out there who can hold to a hundredth of an MOA and produce consistent and repeatable data?
I do believe that flash hole diameter makes a difference, but this was only determined by shooting a small batch of WW2 30-06 brass that had extra large primer holes. I don't know if I have the chronograph data anymore, or if I took it, but it is my recollection that there was a difference.
