I'm sure others will chime in, but here is my experience. With the WO upper, the front sight base is not secured to the barrel with through pins like a normal military rifle M16/AR variant, it is secured by opposing set screws in the location where the normal pins would be located. What is usually meant by zeroed, is that the front sight base assembly is positioned, by loosening and tightening of opposing set screws on the base, so that the front sight is centered with the rear sight set a mechanical zero or dead center. Some brands of rifles will not shoot dead center with the rear sight set dead center, but only with several click left or right added. This is fine for some people, but if you shoot longer distances and are exposed to crossing winds, you may end up running out of left or right windage adjustment if you had to move the rear sight away from dead center just to get on target.
The rifle should be close to zero at 200 yards on a standard highpower target with the elevation wheel set somewhere between 5 and 12 clicks off mechanical bottom. If it is not, you can adjust the front sight to get there by screwing the front sight up or down as needed. With the WO upper, be sure to loosen the set screw under the front sight post before attempting to move the front post. It is there to prevent inadvertant movement and lock the sight firmly in place. Loosen the set screw and then move the sight up. If you need to move it down, you will have to move the set screw down as well. It can be accessed with a standard allen wrench from the bottom of the front post thread hole directly under the front post. Once set for the elevation hold you desire, 6 o'clock or center mass, retighten the set screw under the front post.
The actual performance of the rifle with a specific bullet weight needs to be verified by you. If the barrel is 1-8 twist or faster, it should shoot 68, 69, 75, 77, and 80 grain bullets accurately once you have worked up a load for it. They will also shoot lighter bullets in most cases, but you trade long range wind performance when you use lighter bullets. Some clubs don't even allow you to use 55 grain bullets at the 600 yard line during matches because of poor performance. Most shooters set the 200 yard zero around 10 to 12 clicks off bottom with their favorite load so that if they ever shoot a reduced course at 100 yards, there is enough elevation to lower the rear sight to just a few clicks off mechanical bottom to be on target.
So my routine with a new rifle is to take a "standard load" that I use for highpower, and set the rear sight to 12 clicks off bottom and shoot. Then adjust the front sight until the point of impact is where I want it on the target. Then lock the front post down and I am ready to go. The windage should be correct or just a click or two off if the wind is calm and I am steady that day. Then I can shoot farther distances as needed to ge tthe proper come ups.
Doug Giraud
Giraud Tool Company