In 100/200/300 yard Group Shooting Competition, the 6PPC is by far the dominate Chambering.
In 100/200/300 yard Score Competition, the 30BR, or one of it's variants, is the dominate player.
When I say 6PPC, I am referring to the round that is made by neck turning and fireforming a Lapua 220 Russian case in order to arrive at the final dimensions. There are variants of the "6PPC", some prefer the web area to be a tad different, some even change the shoulder angle. But all have one thing in common. They start with a Lapia 220 Russian case.
Yes, Norma makes cases that require nothing but perhaps neck turning. But at most matches, including National Events, I would venture a guess that 99 percent of the shooters are shooting a 6PPC, and the overwhelming majority are starting with a Lapua 220 Russian Case.
In score shooting, while the 30BR is probably the dominate round, there are other chambering used. They all share one thing in common, the ability to push a typical 112/118 grn 30 caliber bullet at 2950/3050 FPS and Agg at a sub .200 accuracy level.