Some people claim to have better results with a pressure point, but I've floated the barrel on dozens of 77 MK-II's, and also 77 22's, and 77 22 Hornets. In every single case, I've seen an improvement in accuracy. In several cases I've seen horrible groups shrink to extremely tight groups with no other modifications other than the barrel floating. These rifles seem to benefit from free floating, and bedding the action more than any other design I've ever worked with.
As always though, shoot it first. I've also seen 77's that shot real good right out of the box.