Hi CJ
The AFS heads are pretty accurate in their tolerances and I would be surprised if they are heavy. They are 60 grains apart in difference, so go from 340, to 400 to 460, 520, 580 and 640 grains. Each line has a tolerance of plus or minus 20 grains and everyone I test is far, far closer than 20 grains to the stated weight.
I don't know the Scierra Sweep rod, but if it is more of a #9 than a #10, go with the 8/9. If it is more of a #10 than a #9, go with the 9/10 AFS.
I hope that helps.
Cheers
Simon