to xmattmacx and others who have never shot SKS at 200 meters, this is my suggestion (not that i am an expert) on how to calibrate your sights. It is easier done, than read or written.
Since the gong will be shot from the bench, hitting at 200 is not really a big deal if the rifle is zeroed correctly. Even with CZ surplus ammo. You will most probably need a front sight adjustment too. The procedure is this:
1. Set your SKS rear sight to "1". This is the correct setting for 100 meter shooting.
2. Set a target at 25 meters. Use a 6 o'clock hold. This means that your sight picture should be front post aligned with the rear notch, and place the bull on top of your front sight.
Shoot at least two 5-shot groups. Use your FS adjustment tool if necessary to bring your Point of Impact along the horizontal plane, as close as you can to your Point of Aim (the bullseye or center of the paper). In the vertical plane, as long as you are hitting within the 5 inch bull, that is fine.
Then, move farther to a 50 meter target. When satisfied you can hit the paper at 100 meters, move out to 100.
3. At 100 meters, shoot two 5-shot groups without making any front or rear sight adjustment.
Always use the 6 o'clock hold because at 200 meters, the 10 inch gong will look proportionally the same as your 5 inch bullseye. If you use the Center or Zero hold, you will cover the bullseye or gong and cannot see what to hit.I cannot emphasize this sight picture enough. I am assuming here that your shots are hitting paper.
Using you FS adjust tool, bring your POI to POA. Meaning adjust your POI to the center of the bullseye.
Try to obtain a minimum of 5 inch center to center groups. I have seen many who can do 4 inch after a few boxes of ammo.
4. If you have followed the procedure:
Your rear sight is set to "1". Rifle benched, at 100 m, you are grouping around the center of the 5 inch bullseye, and you used the 6 o'clock hold.
If you can group 4 inches at 100 meters, you should easily hit the 200 meter gong 5 out of 10 shots. I have a paper target with 5 out of 5.
5. To prove to yourself you can do it:
Set your rear sight to "2". Using the same 6 o'clock hold, draw a 10 inch bullseye and set at 200 meters. With decent eyesight, good lighting, good shooting technique, you will hit the target.