This is how your pvp rotation should go:
Grav round, grav round Grav round, high impact bolt, grav round, grav round, grav round, high impact bolt.....and so on.
Charged shot and full auto are poor damage in comparison.
The only time you ever use charge shot is when someone interrupt and blocks your grav round. Then you use grav round as soon as you can.
NEVER use hammershot as a gunnery spec. Only if you're on the move and have thrown off a grenade.
The only spec where you'll use hammershot is assault or medic.
For single target damage grav round then HiB is god. Everything else is just a waste of ammo.