When you zero, do you account for the distance between bore and sight?

[ourTINman]

Lets say you have an sight on your gun and the zero of the sight sits 2" above the center of the bore. When you zero at 100 (or whatever) yards do you keep that offset? Do you aim at bullseye and ensure that impact is 2" below?

[theLBC]

no

the farther out you're shooting, the less this matters.

[damon1272]

Thinking this all too hard. Your zero if that is what you want to call it at 100 would be the impact and the spot you are aiming.

Compensating for bore height comes when you have multiple zeros such as 50 and 200. Inside 50 it will hit low. The closer to the target the sight bore offset comes into play. Past 50 and to 200 the impact will be high and past 200 will drop. Just depends on what you are chasing after. This applies more to an AR than a sporting rifle.

[PartyBarge]

Put target where you want.

Put rifle on a stand, aim at bullseye. Fire 1 shot.

Adjust sights to where bullet hit target. Fire 2nd shot. Make minor adjustment.

You are now sighted in for what 99.99% of us need.

[The War Wagon]

no

the farther out you're shooting, the less this matters.

True. For CQB, I sight 'em at 50', and then PRACTICE, to find out what my holdover is, from 50', in.

[gpark09]

Well, it looks like every one answered well.

[ojisan]

Put target where you want.

Put rifle on a stand, aim at bullseye. Fire 1 shot.

Adjust sights to where bullet hit target. Fire 2nd shot. Make minor adjustment.

You are now sighted in for what 99.99% of us need.

While this saves on ammo costs, it does require a stand that will hold the rifle in the exact same place for at least a few shots.
If you can rent or borrow such a stand, the cost may be worth it.
Otherwise you are buying an expensive stand to save the cost of a few rounds of ammo.
The stand also needs to be anchored solidly in place.
Maybe bolted to a concrete shooting table or weigh it down with lots of sandbags, but any way you secure it, more stuff is needed.

The idea is simple, the devil is in the details.

To the OP's question, yes, you do have to account for the height difference, especially with handguns and red dot sights.
If you sight in for 25 yards, up close you will have to aim a little low.

[BrassCase]

OP, remember that bullets don't travel flat, they have to be arced to hit targets as they move further away. There is an angle created from the barrel to the target and back to the optic. Lay it out on paper and it will become easier to understand.

[kcheung2]

Zero means zero. It doesn't mean 0+2.

I don't think you understand the concept. Zero means the distance that the point of aim (which is a perfectly straight line, for an AR approx 3.5" above boreline) intersects the bullet path (which is a curve). The term "zero at 25 yards" means that the point of aim (let's say a scope) is pointing perfectly horizontal & the gun is pointed slightly upwards so that at 25 yards, those 2 paths intersect. So if you're a very good shot & very stable, then all your holes will be in exactly the same spot, right in the middle of your crosshair. If you adjusted +2 (or -2) then you're not actually zero'd.

There are some diagrams that depict this, but for some reason illustrate the gun as perfectly horizontal also, which leads to the mistaken idea that bullets travel in an upward path from a horizontal barrel. They don't.

Some people do add an offset, but it's for a specific reason. For example, when I sight in a rifle, I go to the 25 yd range and shoot 1.75" low. In other words, if my scope is perfectly on center I want my hits to be 1.75 lower. The reason for this is because my final goal is to actually zero at 100yds, but 25 lets me do the rough tuning and I know that with a 100yd zero, at 25yds the bullet path is still 1.75 below point of aim.

Another example is lets say I want to zero at 200 yds, but my range only goes out to 100. So I will shoot 2.2" higher than my point of aim, in other words I want the holes to be 2.2" higher than my target crosshair. Going back to the diagram visualization, the gun/barrel is pointed slightly upwards so the bullet is tracing an arc, at 100yds it's near the high point of the arc & at 200 it drops back down & intersects the point of aim.

[subscriber]

Tinman,

Much of zeroing is personal preference:

You can type in values into this Hornady ballistics calculator to see what happens to height of point of impact at various ranges, when using particular scope above bore heights, and zero distances. You can assume calibers, BC and other variables such as velocity; as this is just for the purpose of illustration: https://www.hornady.com/team-hornady...alculators/#!/ Scroll down to calculator.

And yes; zero generally means that the bullet hole appears where the sights were, at moment of discharge. At least, that is the general intent. Then the argument start as to whether a 100 yard zero is better than a 200 yard zero, or 250...

As the bullet usually cross the line of sight twice on the way to the target, a 15 yard zero could also be a 250 yard zero. This is caliber, load (BC) and barrel length (velocity) dependent. And is affected by scope above bore height.

[JCHavasu]

There are some diagrams that depict this, but for some reason illustrate the gun as perfectly horizontal also, which leads to the mistaken idea that bullets travel in an upward path from a horizontal barrel. They don't.

Yes, I have had a few friends try to tell me that a bullet is rising when it leaves the barrel. No, the bullet comes out perfectly horizontal to the barrel and immediately begins to drop. Thus we compensate by pointing the barrel up slightly to hit where we want to. That portion of the whole thing is really not complicated.

[subscriber]

Yes, I have had a few friends try to tell me that a bullet is rising when it leaves the barrel. No, the bullet comes out perfectly horizontal to the barrel and immediately begins to drop. Thus we compensate by pointing the barrel up slightly to hit where we want to. That portion of the whole thing is really not complicated.

You are arguing with yourself. By pointing the barrel up to compensate for drop, the trajectory follows a rising path, before it follows a lowering path.

As such, bullets fired at targets situated at the same level as you, do in fact rise after they leave the muzzle. If they did not, they would strike low due to gravity.

Your interpretation that bullets experience lift as if they are wings is not the point you are arguing against. However, bullets due experience lift under certain crosswind conditions. So, if you want to act like a know-it-all, know it all.

[bombadillo]

Ninety-nine times out of a hundred, I will physically look down the bore with the gun in a rest, look at exactly what it's pointing at approximately 25 yards out, zero my scope to that, take it to the range at a hundred yards and see how far off I am. Usually I'm within a few inches of what I'm aiming at. Not a very glamorous way to bore sight but it's worked for years

[ysr_racer]

My Savage Axis in .270 Winchester is zeroed in at both 25 yards and 200 yards at the same time. Something about bullet drop and the distance of the scope over the bore.

[QED]

Your bullet’s trajectory isn’t like a laser so of course you need to compensate for the scope offset to barrel! I‘m tempted to insert a snarky remark here but I will resist. Good luck with your search for info.