[tundragriz]

2F is more common for 50 but recently FFF seems to be popular because it can also be used in the pan. 3F burns faster/hotter so reduce a 2F load by about 10% for 3F, I usually figure about a 10gr reduction. 90gr of FFF would be about a max load. In my Hawkens I shot 2F and 4F pan.

http://www.goexpowder.com/load-chart.html