oldracer,
The Walker was sighted-in for 50-75 yards, probably closer to the 75 yard mark! Obtaining the same identical sight picture with the same amount of front sight/back sight alignment each time will narrow your groups down some. My Walker is exactly 6.5 inches high at 25 yards, so I merely aim the revolver 6.5 inches lower than the "X" Ring and I'm hitting in the 90's!
I would recommend shooting the big wheelgun with BOTH HANDS, at least until you get "the feel" for how much front sight to use!
The Walker I have is a great shooter, and is dead-on side to side. On several occaisions I've hit the 135 yard gong (man-sized torso) at one of the BP clubs that my Son & I belong to. I'm currently using it for the NRA Black Powder Pistol Qualification Matches another one of the local clubs that I belong to is running. So far at 50 yards, I've scored 38 points more than the single-shot guys, but not all of them have competed yet.
Here's hoping you have as much fun with yours as I do with mine!
Have a good Turkey Day!
Dave