I've been fooling around with "buckshot" loads for my Navy Arms 12 ga SxS and have found that 3 .454 dia lead round balls make a deadly load out to 30 yds. I'm going to try 4 .440 balls.
Is your 10 ga a modern "traditional" style gun, a modern inline or an oldie?
Some friends of mine with modern inlines are using 2 oz of shot for turkeys.
A nice light load for a 10 ga is 100 grs FFg with 1 1/4 oz of shot.