The problem is at long range it is affected by the wind to much, and the lethality at long range is not good enough IMHO. Oddly enough go up to the 6.5 and it is much better bc and lethality than you would expect from such a small round. Why? Lots of theries but no one knows.
The 6mm PPC was a wildcat cartridge developed in Europe by Lou Palisano and Ferris Pindell. Its a short stubby cartridge used for bench rest shooting. Its a VERY accurate round. I have alot of experience with the 6PPC and the reason that snipers don't use this round is for the two following reasons. #1 it is very suceptible to wind at much longer ranges and #2 since it was originally designed as a bench rest cartridge, bench rest shooter normally shoot anywhere from 100-300 yards max. Hope that answered some questions.