what 6mm are we talking about? i shot a 6CM for a few years and my choices would be...
#1 115g DTACS
#2 105g berger hybrids
#3 107g SMKs
#4 108g ELDMs...i have not shot the 108s personally but i do know a guy that is and loves them.
the 105 hybrids were always just a tiny bit more accurate but the 115s at 3050 are hard to beat plus there is not doubting if you hit or miss steel at longer distances...they hit almost as hard as a 6.5 bullet.