Tried to Google it or ask for people to explain it but no luck.
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Bullets do not fly straight. Gravity affects them and pulls them down.
So if you are far enough away the gravity is going to have a significant effect, you cannot aim directly at what you want to hit. You have to aim high, and how high you have to aim depends on how far away the target is.
To zero in and fix for elevation means to calculate how much gravity is going to impact your bullet and it’s flight and adjust the site so it is high enough that the target will get hit.
A gunsight looks in a straight line, light just works that way. Bullets move in a shallow curve, gravity just works that way. So, the first step to alignment is to adjust the scope so matches exactly where the bullet goes at a fixed distance, like 100 yards. You do this on a calm day with a target at 100 yards. You aim at the center of the target and fire. The bullet hits the target someplace else, and you turn tiny screws to adjust it. When the bullet hits where you are aiming, it’s “zeroed”. When shooting at different distances, you can turn clickwheels on the scope to compensate for the distance being ≠ 100 yards. These adjustments are called elevation. There are also special reticles (lines that appear when you look through the scope) that can be used for this. You need to know the distance, thus they sell laser rangefinders. You can also adjust from side to side with a clickwheel, what’s called “windage” because you are adjusting for the wind.
Zeroing is the process of determining or setting where “zero” is on the scope when attached to the weapon and used by the firer. There will be manufacturing variances in the scope, and everyone holds their weapon differently. Zeroing generally entails the user firing several sets of 3-4 rounds and making adjustments on the scope so that those shot groups are in the center of the sight of the scope (zeroed)
Elevation is the practice of adjusting your aim to take into account the flight path of the bullet. Depending on range to the target, you may need to adjust your aim up or down to account for the fact that bullets travel in an arc, not a straight line, due to gravity
And, you didn’t ask, but there’s also windage. Aiming left or right due to (as the name suggests) wind.
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Zeroing is when you adjust the scope so that the rifle it is attached to is accurate at a certain distance. You cannot have a scope be accurate out of the box, you have to adjust it for your rifle and your scope mount height, among other things.
You also cant be perfectly zeroed and accurate at all distances, that doesn’t exist because of “height over bore” and also bullet drop. And other factors like type of ammo but let’s keep it simple.
So you choose a distance that you prefer for your use case. It’s common for carbine and smaller rifles (think AR) to be zeroed to be accurate at something like 50m or 100m. For a long rifle you only plan to use for longer distances, you may zero longer distances.
Elevation and Windage are two adjustments you can make “on the fly” to adjust for a particular specific shot. So you lock in a general “zero” at say 100m, but now you are going to shoot out to 500m. You dony re-Zero your scope every time, that would be way too silly and time consuming. Instead, long scopes have knobs on them for Elevation and Windage. elevation allows you to temporarily adjust the scope upward or downward for longer or shorter shots from your zero. Windage allows you to temporarily move your scope left or right, to adjust for wind that is out in the flight path of the bullet.
After the shot, you can easily undo the “click” adjustments you made to elevation and windage to get back to your “zero” position.
TL:DR – zero makes your scope accurate for your rifle and ammo at a specific distance. Elevation and Windage allow for temporary adjustments for specific shots in various conditions
Okay, let’s try to keep this simple:
On a weapon, all firearms but also some bows / crossbows, you have a set of sights that allow you to aim and send the bullet or arrow where you want it to go. Every weapon comes with basic sights, on in front and one in back. Aligning both of them to form a ‘sight picture’ with the target is how you aim and shoot precisely.
Adding a scope to a weapon means that you’re adding a component that wasn’t installed and calibrated by the manufacturer of your weapon. Consequently, if you aim through your scope without calibrating it first, which is called ‘zeroing’ a scope, the bullet or arrow isn’t going to land where you’re aiming.
So how do you zero a scope? It’s actually extremely simple:
First, you attach the scope securely to your weapon so that it doesn’t move. At all.
Second, you rest your weapon on some sort of fixed rest (sometimes called a bench rest) so that you can aim and shoot it without the weapon moving, which is what would happen if you were just holding it in your hands. This is crucial to figure out how to adjust your scope based on where the bullet lands after firing.
Third, you shoot one round (bullet). After the bullet hits the target, you check the target to determine how far off from where you were aiming (generally dead center) the bullet hit the target.
This can be measured in metric units (MIL – millimeters) or in imperial units (MOA – minutes of angle) . By how much in either unit (MIL or MOA) your bullet hole is off relative to the center of the target tells you how to adjust your scope in elevation (up or down) or windage (left or right).
Then, you use the elevation or windage dials on your scope to adjust your scope so that the point of impact (where the bullet should go) matches where your weapon is sending it based on what you see through your scope.
After you’ve made the adjustments, you shoot another round into the target to check that your adjustments are correct. If the bullet hole is still off relative to the center of the target, measure the offset again and adjust the windage and/or elevation again on your scope.
Repeat this process until every shot you fire goes exactly where you’re aiming.
Once the process is complete, your scope is conseidered ‘zeroed’.
Bullets follow a ballistic trajectory. They fall due to gravity, and can be blown off course by the wind. For this reason, gunsights are adjustable in two ways: windage (left/right) and elevation (up/down).
“Zeroing” is the process of adjusting the gunsights such that the bullet will land exactly where the sight is aimed at a specific distance (typically 100m) on a calm day with no wind. This ensures that the gunsights are accurate in most cases. However, when the wind is blowing the bullet may land slightly to the left or the right of where the sights are aimed. When the target is closer or further away than the range the sights have been zeroed at, the bullet will land slightly above or below where the sight is aimed.
This is why many scopes & sights can typically adjust windage & elevation on the fly with a set of knobs or sliders. Gravity & wind both have a much more pronounced effect on bullets at longer ranges, and sights must be adjusted to remain accurate when engaging targets at different ranges. This is a big part of why snipers have spotters. The spotter will measure the wind and the distance to the target, do the math, and tell the sniper what adjustments need to be made. Some advanced modern scopes can do this automatically to an extent.
There are also more variables than just wind & gravity, but those don’t have a significant enough effect to matter at typical engagement ranges, and only need to be accounted for at long range or when a high degree of accuracy is nescessary.
Edit: typo
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