I could not agree more with Frank21, the 160gr up bullets are superior for long range shooting because of the B.C. advantage. The 139gr SST you speak of has a B.C. of .468 the Berger 168gr VLD has a B.C. of .643 and the Berger 180gr VLD is .684 a vast advantage. the 139sst's are fast and flat at close to medium range but pale in comparison at long range.
UB
p.s. "calibre is normally a frenchie or Euro term, in America it is caliber, but then again they just changed the name of the mall down the street to the "Town Centre". guess it sounded more elegant than town center.