Albaro, yes, 168gr through 180gr is optimal in .308. A heavier bullet is longer and has a higher ballistic coefficient and will shed velocity slower than a lighter bullet for targets beyond 600 yards. A heavier bullet will also be more stable in cross winds compared to lighter bullets as well.

I left a lengthy response to only be sent for review for whatever reason. In short, 168 grains is what I use but you have to figure out what your rifle likes best.