The Tall Target Test: Does Your Scope Actually Track?

Dial ten mils for a thousand-yard shot. If your scope tracks four percent short — and plenty do — you just moved 34.6 inches instead of 36, and your bullet lands about fourteen inches low. Nothing about your solver was wrong. Your muzzle velocity was right, your BC was right, your atmospherics were right. The turret simply did not deliver what it promised.

Here is the part that should bother you: a two percent tracking error hides completely inside normal group dispersion. You will never see it at 100 yards. You will never see it in a five-shot group. You will only see it as a rifle that mysteriously shoots low past 800, and you will spend a season blaming your load, your chronograph, or your solver for a mechanical fault in your optic.

The tall target test finds it in about twenty minutes and ten rounds.

What the test is

You put a very tall target at 100 yards with one true-vertical line down it. You zero at the bottom, dial a large, known amount of elevation, and shoot again at the same aim point. Then you measure how far the group actually moved with a tape measure.

The distance it should have moved is simple arithmetic. The distance it did move is a fact. The ratio between them is your correction factor, and it applies to every solution you will ever dial with that scope.

Why scopes do this at all

A riflescope turret is a mechanical assembly — a threaded erector, springs, and detents — manufactured to a tolerance. “0.1 mil per click” is the design intent, not a measured guarantee. Manufacturing variance, spring pressure, and where you are in the erector’s travel all move the real value around. A scope that tracks within one or two percent is good. One that cannot hold four percent is genuinely poor, and the only way to know which one you own is to measure it.

This is not a cheap-scope problem, either. It is a this specific scope problem, and expensive glass is not automatically exempt.

How to run it

1. Hang the target truly plumb. Confirm the vertical line with a plumb bob or a level. Do not trust the target frame, the backer, or the fence post — if the line is not plumb, you will read cant as a tracking error and chase the wrong fault.
2. Laser the actual range. The maths depends on real distance. A range you assume is 100 yards but is really 102 will skew the answer by two percent, which is the same size as the error you are hunting.
3. Confirm your zero on the aim point at the bottom of the sheet.
4. Dial up a large amount — at least 30 MOA or 10 mils. Bigger is better, because measurement error gets divided by the distance travelled. But stay away from the ends of the turret’s travel, where tracking is least linear.
5. Fire a group at the same aim point as before. Do not chase the reticle up the target; the whole point is that the turret moves the impact, not your aim.
6. Measure centre-to-centre with a tape, from the first group to the second.

Reading your result

Two lines of arithmetic:

Expected shift = dialled × range × constant
Correction factor = expected ÷ actual

All four return inches. A worked example: you lasered 102 yards, dialled 30 MOA, and measured 29.8 inches of movement. Expected is 30 × 102 × 0.01047 = 32.04 inches. Your correction factor is 32.04 ÷ 29.8 = 1.075. To truly get 30 MOA out of that scope, you dial 32.25.

Enter that factor in your solver — Apex Ballistics and most others carry a sight-scale or tracking-correction field — and every future solution comes out already compensated.

If the group walked sideways

If your second group is not just high but noticeably left or right of the first, you did not find a tracking fault. You found reticle cant, or a target that was not hung plumb. Fix that first and re-run.

The companion test

The tall target test measures how far your clicks go. It says nothing about whether the turrets are square to each other, or whether the scope comes back to zero after you dial around. That is the box test: five shots, holding the reticle on one aim point the entire time while the turrets walk the impact around a square and back. If the fifth shot does not land on the aim point, your scope does not return to zero — and that is arguably worse than a scale error, because it is not correctable with a number.

What it costs you to skip this

The expensive part is not the fourteen inches. It is what you do next.

A shooter who has not run this test sees a miss at long range and starts “truing” the solver — adjusting muzzle velocity or BC until the prediction matches the impact. It works. The solution is now perfect at that one distance. But you have taken a mechanical defect in your turret and buried it inside a physics variable, and physics variables do not behave like turret errors. Your falsified velocity now corrupts your wind holds and your energy numbers, and the error re-emerges — differently — at every other distance.

This is why the order matters so much. Verify the scope, then true the solver. Do it backwards and you spend the season fighting a solution that is right at exactly one range and wrong everywhere else.

What it changes for you

Twenty minutes of work buys you the ability to trust your own dial. When you come up 8.4 mils, you know 8.4 mils is what arrives at the bullet. Every subsequent piece of data you collect — drops, DOPE, truing — is being measured against a known reference instead of an assumption.

That is the real return. Not the fourteen inches. The fact that from here on, when something does not match, you can be confident the problem is somewhere you have not looked yet — instead of wondering, every single time, whether it was the scope.

Next: how to true your solver properly — and why truing at 200 yards can inject 80 inches of error at 1000