Some barrels will shoot the heavies better than others, although you still need to push them hard. my 1:9 SPS Tactical will not shoot the 75gr A-Maxes better than 1.5MOA, however, it averages just over half MOA with the 69gr Matchkings.
my 1:9 shoots a 77g ncc very well.even the 75g berger vld.but one will have to remember that what might shoot in mine may not in yours.so get a couple of diferent weight bullets and go shot.but hey its JMHO