Because in killing and seeing killed huge numbers of animals by large numbers of people from world class to rank beginners no one has performed better with “the biggest cartridge you can shoot accurately”. Well actually, that’s exactly what works, the problem is the largest gun nearly everyone can shoot “accurately” is about 15 ft-lbs of recoil. This isn’t a guess- I have seen well over one hundred different people (including about two dozen from this forum) in the last year shoot in varied mountainous conditions in the western US in the last year. Not one hit more targets out to 800 yards with 300 win mags and 300prc’s than those exact same people did with 6mm creedmoors. Not one. People lie to themselves about how well they shoot guns, or simply have no idea what they actually do on demand with guns in novel terrian.
Ok we can make this easy. Please list every elk that you have killed with your 300 PRC and 215gr Bergers, the range, presentation, impact location, the bullets performance, and the exact reaction that the animal gave. Then list the same for each you have killed or that you have directly spotted for being killled with 223’s, 6mm’s, and 6.5mm’s- giving all the same information.
I will do the exact same- 20 elk last year from 80 yards to 803 yards, and from 223’s to 300 PRC’s. 16 elk the season before from 80 yards to 984 yards, and from 223’s to 300 PRC’s. 14 elk the year before from 197 yards to 735 yards, and from 223’s to 300Win mags. In every year there are kills with .224, 6mm, 6.5mm and 30 cals. If you want we can go back more than three seasons that have just as many elk killed and have 25, 27, and 338 cals included.
If they all run off after a miss- who cares? It’s when you make a poor shot, or even a good one and can get follow up shots in the animal because you saw the impact and learned from it.