The answers are getting better, BUT! it goes back to the case and its ability resist sizing, there is no neat and tiny bundle of words that explain “EVERYTHING YOU EVER WANTED TO KNOW ABOUT RELOADING AND SIZING A CASE” (Johnny Carson and ED McMahon).
A reloader can determine if the case won or the press won before lowering the ram, If the case has more resistance to sizing then the case can overcome the press won. If the case wins the die does not make it to the shell holder, the part of the case that prevented the die from making contact with the shell holder can be measured with a feeler gage, in thousandths.
Bench rested rifles are built be be bench rested, bench rested rifles are different from most of my rifles, I have a few very accurate rifles, it is not easy to improve on their accuracy, again, accuracy depends more on an accurate rifle than accurate ammo. I have one rifle I do not load for, the accuracy can not be improved upon, DIFFERENCE!? the chamber in the store bought/over the counter rifle has a chamber that was built for factory ammo without the tolerance. The case when chambered hits at the belt and the shoulder at the same time. Cases fired in the rifle chamber in a chamber gage with very slight thumb pressure.
Again, I have neck sizing dies, I have small base dies, I have forming dies for the 300 Win Mag. I have another 300 Win mag, it shoots patterns A very disciplined reloader offered to load for the rifle in an attempt to determine ‘what it liked’, he gave up, I sent the rifle back, same ammo, one rifle shot one hole groups, the other shot patterns.