That front sight was designed for use in Metallic Silhouette shooting, an event where full size steel animal silhouettes, 10 of each are placed at, if I remember correctly 50 meters (chickens), 100 m. (turkeys), 150 m. (pigs) and 200 meters (rams).
So the idea is to set each of your 4 front sight elevations for each of those distances. I don't know the allen key size but one key in my allen set fit.
Of course, you can always decide for yourself at what range to set each position.
To set your sights, actually easier to do it than write and read this instructions:
1. Unload the revolver. Keep cylinder open.
2. With the barrel pointing away from you (still in safe direction), look down on the front sight. You will see the four allen set screws, numbered 1,2,3, 4.
3. Below the allen screws you will see the adjusting wheel, which has 4 positions as indicated by numbers you can read by looking down at the left side of the wheel.
3. Familiarize yourself with the adj. wheel by turning it. It is easier to turn it if you depress the rear portion of the plate holding the four allen screws.
You will see that each position of the wheel is numbered 1 to 4, on the left side. Notice the cutout on the sideplate, to allow clearance so you can read the small numbers.
4. Pretend you are at the target range. Say you want to set position (1) for the 50 m. chickens. Turn the wheel so you can see position (1). Zero your elevation by adjusting allen screw No. 1.
5. Do the same for wheel position 2 to 4.
6. Once you figure out the procedure, go to the range and calibrate for your 4 distances.
I was going to adjust the sight on my 686 silhouette for 25 m, 50, 75 and 100meters, but mounted a red dot instead.
