Mossberg,

60 yards with #4 on geese? Uh, er, no offense my friend.... The geese will laugh at you when you take a shot.

I too have a Remington 870 Express Magnum (lefty 12GA). For geese, I was told to get some 3" Magnum shells in steel BB size and use a full choke. They will hit effectively out to 40 yards, which is about max for a full choke.

Hope this helps.

Butch