There's nothing wrong with sticking with 777 - it's my favorite powder. I know a lot of guys swear by BH209 but I just can't justify the price, considering I can get 777 for around $15 a pound on clearance. I don't have any personal experience with Pioneer Poweders, but I'm sure Lane is giving good advice here.

If you stick with 777 I would recommend trying FFFG if you can find it- it's always been more accurate for me, produces less crud ring, and gives higher velocities with the powder charges most people use. Personally I don't like Pyrodex- it's very dirty and produces lower velocities.