In 2003-2005, they seemed to use Superdome.
In 2006-2007, they used H&N FTT, which are usually much more efficient, but still not as efficient as the Penetrators, JSB/Daystate Heavies and the like.
Nowadays, I think they're using HW FT Special, which are fairly similar to - but slightly heavier and better than - the FTT.
In my experience, those pellets are fairly good for power-setting the .22 versions, but in the .177's, FTT/HW-FTS are not much above average power and often out-powered by the heavies, so the heavies can run close to the limit.