[dangerranger]

You are probably going to be happiest with the lightest bullet your gun will shoot well. By using that it will be fast, and cause a lot of shock to a smaller animal. The next thing you need to look at is the bullet. It needs a thinner jacket to open in a thin skinned animal.
I'm using a 6.5x55 so very close to 6.5CM. The lightest bullets I have been successful with are 140 gr. But I'm using a military barrel, that was made for 175 gr bullets.
Speer makes a 90 gr TnT, Nosler has their Varmageddon, and Sierra makes a Varminter bullet that all have thin jackets. These bullets should be good to around 3000 fps. after that you will just have to test to see that they don't come apart on first contact. [that would make a big hole] You may have to experiment a little to find what your gun likes best. God Luck, DR