Does Your Scope Track?

A zero tells you one specific thing: with the turrets at their current setting, your line of sight and your bullet's path cross at one distance. It says nothing about what happens when you turn the dial. Tracking is that separate question — when you dial 10 mils of elevation, does your point of impact actually move 10 mils, or something close enough to it to trust at distance?

Answering whether your scope tracks requires a dedicated test, because a zero cannot answer it. You can zero a scope perfectly at 100 yards and still own turrets that move the reticle 9.7 mils for every 10 you dial, that move unevenly across the travel, or that fail to return to true zero after a big excursion. None of that shows up in a zero — a zero only exercises the turret across the tiny correction needed to center a group.

⚠️ Most scopes track close enough to their marked value to be trustworthy. Some are off by a small, consistent percentage — a few percent, commonly. A few are genuinely broken: inconsistent, non-repeatable, or mechanically faulty. You cannot tell which of these you own by looking at the scope, reading the spec sheet, or trusting the price tag — you have to test it. And the error is invisible at the ranges most zeroing and casual shooting happens at; it only becomes large enough to matter once distance multiplies it.

The tall target test needs four things, and skipping any one of them invalidates the result. A tall vertical target, sized with margin for the movement you're about to dial. A verified plumb line — a real plumb bob hung to settle, or a level used to strike a true vertical line on the target backer, not a line drawn by eye, because your eye is exactly the thing you're testing the rifle against. A rifle that is level relative to that plumb line. And a distance that is measured, not paced or estimated.

⛔ The distance must be measured — with a rangefinder or a tape, not paced off or guessed. ⚠️ A 3% error in your assumed distance becomes a 3% error in your measured tracking result, because every calculation in this test scales the expected movement by distance. Get the distance wrong and you get a tracking number that describes your pacing, not your scope — and it looks exactly as convincing as a real one. This is the single most common way people run this test and walk away with a wrong answer.

The rifle and reticle also need to be level to that plumb line, not just to the ground or to your eye. If the rifle is canted even slightly, dialing 'straight up' elevation actually moves the point of impact along a line tilted from true vertical, and some of that movement shows up as horizontal drift instead of vertical. The mounting and leveling work is its own job — get the reticle level before you start, because this test will faithfully report cant as if it were a tracking error, and the two look identical in the result.

1. Aim at a mark near the bottom of the tall target and confirm you're on your established zero — this is your aiming point for the whole test, and you will not move it. 2. Dial a large, known amount of elevation up — large enough that the expected movement is many inches, not a fraction of an inch. 3. Without touching zero again, aiming at the same mark, fire a group — several rounds, for the same reason you shoot a group to zero rather than trusting one shot. 4. Measure the vertical distance from your original aiming point to the center of the new group; this is your actual movement. 5. Dial back down to zero and confirm you're back on the original mark before you do anything else with the rifle.

🎯 Dialing a big number is what makes the test sensitive. It turns any real tracking error into a large, easily measured distance on the target rather than a fraction of an inch buried in group size and measurement noise.

⚠️ A 1-mil test measures your ruler, not your scope. The expected movement is barely more than three and a half inches at 100 yards, and by the time you've accounted for the width of your own bullet holes and a small aiming error, the 'error' you measure is mostly noise. Dial something you'd actually use at distance — several mils, not one — so the signal is bigger than the measurement error around it.

Convert the dialed amount to an expected movement in inches at your measured distance — one mil is 3.6 inches per 100 yards of distance, one MOA is roughly 1.047 inches per 100 yards — and compare that number against what you actually measured on the target.

🎯 The result is a scale factor: your actual movement divided by the expected movement. Dial 8 mils, expect 28.8 inches of movement at 100 yards, measure 27.9 inches actual, and your scale factor is 27.9 / 28.8 ≈ 0.97 — the scope is tracking at 97% of its marked value.

⚠️ A small, consistent scale factor error is not a reason to condemn the scope. A scope that reliably tracks at 97%, or 103%, of its marked value is entirely usable — you correct for it in your ballistic solver, either as a custom click value or as a scale applied to every dialed correction, and from then on the scope's honest quirk is baked into your data instead of working against it. What actually condemns a scope is inconsistency: results that don't repeat from test to test, or a scale factor that changes at different points in the turret's travel. A number that's reliably wrong is a solvable problem. A number that won't hold still is a mechanical one.

Step 5 of the procedure above — dialing back down and confirming you land on the original mark — is not a formality. Return-to-zero failure means the turret does not reliably return to the same mechanical position after a large excursion, and that is a worse problem than a scale factor error, because a scale factor is a number you can correct for and a broken return is not. If your dialed-down position doesn't match your original aiming point, the scope has a mechanical fault, not just an imprecise one.

The box test extends the same idea to both axes at once: from zero, dial up a known amount, then right the same amount, then down twice that amount (back past zero and an equal distance below), then left the same amount, then back up and right to return to zero. Fired correctly, the shots trace a square, and the final group lands back on the original aiming point. It checks elevation tracking, windage tracking, and return-to-zero together, and it's worth running alongside the tall target test — the tall target test alone only exercises elevation.

A zero stop — a physical stop built into some turrets that prevents dialing below your zero — and a confirmed mechanical zero both matter here: a zero stop makes returning to zero fast and certain under time pressure, but it's only trustworthy once you've verified the turret actually tracks and returns correctly without it. Set it up, and confirm it, after tracking is verified — not instead of verifying it.

⛔ Verify tracking before you true your ballistic solver against observed drop, not after. Truing works by adjusting muzzle velocity and drag scale factor until your solver's predicted drop matches what you actually measured at distance — and that process cannot tell the difference between the solver's inputs being wrong and the scope not moving the amount the turret says it does. Both look identical: a growing vertical miss as distance increases.

If you true a ballistic solution on a scope with an unverified tracking error, the truing process will faithfully absorb that mechanical error into MV or DSF, and your solver will report a 'trued' solution that only works with this specific mechanical fault present. Change the distance, the load, the ammunition lot, or the altitude, and the balance between the real ballistic error and the baked-in mechanical error shifts — the solution that worked perfectly at your truing distance quietly stops matching reality somewhere else. You will have no way to tell, from the solver alone, whether the new miss is weather, a new lot of ammunition, or the same scope fault reappearing at a different scale.

Run the tall target test — and the box test — before you ever true a solver against this rifle and scope. Tracking verification is the step that must come first, so that when you do true your solution, every correction you make is going into the ballistic model rather than papering over a turret that doesn't move what it says it moves.

Retest whenever something could plausibly have changed the mechanical relationship between turret and reticle. After any remount — new rings, new base, or the same mount removed and reinstalled — because leveling and torque are both redone from scratch and neither guarantees the internals came back exactly where they were. After a drop, a hard knock, or any impact you'd think twice about before trusting the zero itself.

When a dope card that has agreed with reality for months suddenly stops matching at distance, with no other explanation — a wandering scale factor is one of the few things that produces exactly that symptom. And periodically, on any scope you're depending on for a genuinely long shot, whether or not you have a reason to suspect it — cheap insurance against a fault that develops slowly enough that you'd otherwise never notice it.