Not every chip is the same, so just because some guy hits a higher clock than you online doesn't mean your chip will do so.
Have you tried increasing the voltage?
it was the same chip (http://www.sapphiretech.com/presentation/product/?cid=1&gid=3&sgid=1088&pid=1169&psn=&lid=1&leg=0)
<--- That is the same card i have, and i would like to how to increase the voltage, i use MSI after burner, but the voltage is locked so i don't know how to do it, can you please help me.
ps: the voltage on the card is 1.1, i want it to be 1.2 or 1.3