This is mainly for guys like
but, a lot of this is applicable to boltguns and such with Iron sights.
Setup on the rifle- Front sight centered, rear sight windage adjustment centered, Elevation run down all the way then raised eight clicks.
Now, you really need a calm day to do this on. We're going to go through what's necessary to get a 100 yard zero, ranges farther than that will be explained but, it's easy. Set up a 25 yard slowfire pistol target at 100 yards. Trust me on this, it's all math. You'll need to fire from a bench if possible because you need to rest the rifle to do this. Whatever you use for a rest remember; DO NOT REST THE RIFLE AHEAD OF THE SLING FERRULE. Resting the rifle on the front handguard will screw up the sightin. Now, use a six O'Clock hold the front post in the rear aperature centered with the bottom of the bull resting on the top of the post. Think Lollipop. Get a good cheekweld on the comb and fire an eight-shot group without raising your head to see where you're shooting. Just concentrate on shooting the group and hold the same sight picture.
Now, go get the target. Draw a vertical line from the top of the target to the bottom and draw a horizontal bisecting line from one side to the other with both lines crossing in the middle of the X-Ring. Find the center of your group and measure from there to both lines This will give you both adjustments, Elevation and windage to put you theoretically in the X-Ring.
Say that your group-center is three inches low and two inches to the right. This means you need three clicks up on elevation and two clicks for windage but, we're not going to adjust the windage with the rear sight. We're going to make the change with the front sight since it isn't more than four inches. Here's the secret, for every .007 you move the front sight, left or right or by filing down, you move the point of impact 1" at 100 yards. There's a formula for this and I'll add it at the bottom but, trust me, the formula works for any rifle, any caliber.
Okay, to do this you need three tools. An Allen Wrench(3/16ths.), a scribe, and a dial-Vernier or commonly called a Caliper. Scribe a line on one side of the sight on the sightbase of the Gas Cylinder so you can move it back once you loosen the front sight. When you loosen it you'll see why. Take the Caliper and adjust it to read .014 and lock it(.007 times 2). Now, put the tailpiece of the Caliper against the right side of the sightbase and move the front sight to the right until it hits the tailpiece( To move left, you move the front sight to the right. This moves the muzzle left) and tighten the Allen screw in the front sight snug. Remove the tailpiece and tighten the screw down more. There! Your windage is set, now just crank the elevation up three clicks and you're done.
To adjust for 200 yards add two more clicks of Elevation. for 300 yards, add three more clicks. going to 600 from 300 add 12 more clicks.
Sight Correction formula
Sight-radius in inches times 1"( change of impact at 100 yards)divided by range to target in inches.
28" x 1" / 3600= .007"
This works for any rifle and most pistols/revolvers. Just plug in your sight-radius and distance to target in inches. It's also the correct way to zero an M1A.