Question about barrel life

I'm in the process of researching calibers, and their respective barrel life to plan/budget for competition rifle builds. I'll likely start learning the ropes in .308 because it's what I have on hand. I don't expect to be competitive with a lightly modified production rifle chambered in .308, but I want to have real life competition experience before diving into a mult-thousand dollar custom competition open rifle build.

In my research I'm seeing reports of .308 barrels being "shot out" in 10,000 rounds. The caliber I'm interested in eventually graduating to will be in the 6mm family, perhaps 6br. In this caliber I see barrel life reported at 2,000 rounds.

Furthermore, I'm seeing that muzzle velocity for .308 is around 2600fps. Muzzle velocity for 6br is generally around 2850fps. Can it really be that an increase of 250 fps at the muzzle will decrease barrel life by 80 percent? That seems rather remarkable. Surely there are other factors I'm not aware of. If the answer is simply, "it is what it is," I can work with that, but I am in search of a deeper understanding, and hoping for your knowledge. Thanks a bunch.