A solver does not predict where your bullet lands. It predicts how far the bullet has fallen relative to the line your sights already agree on. Move the zero and every single row of the output moves with it. That is why a careless zero is not one small error — it is a constant offset applied to every shot you will take with that rifle.
What a zero actually is
The bore points slightly upward relative to the line of sight. The bullet leaves below the sight line, crosses it on the way up, arcs over, and crosses back down at the zero distance. There are always two crossings — a near one, usually somewhere around 25–40 m, and the far one you chose.
That near crossing is why a rifle zeroed at 200 m still hits close to point of aim at 30 m. It is geometry, not luck, and knowing it exists stops people from re-zeroing at short range in a panic.
Choosing a zero distance
| Zero | Best for | Trade-off |
|---|---|---|
| 100 m / 100 yd | Anyone using a solver | Requires dialling or holding for almost every shot |
| 200 m / 200 yd | Hunting inside 250 m | Mid-range rise of a few centimetres above the sight line |
| Point-blank (max ordinate) | Fast field shooting, no optics work | Awkward reference for a calculator; the zero is not a round number |
| Zero further than 200 m | Rarely useful | Large mid-range rise; you must remember to hold under |
If you intend to use ballistic software at all, zero at 100. It is the least ambiguous anchor, the easiest to confirm precisely, the least affected by wind and mirage, and it is the distance at which a small angular error translates into the smallest linear error on paper. Every correction in your DOPE then reads as a clean positive number.
How many rounds it takes
More than three, and fewer than you think if you are patient. The problem with a three-shot zero is that you are trying to find the centre of a distribution from three samples, and your group size is usually larger than the correction you are chasing.
- Get on paper at 25 mTwo rounds. This is not a zero, it is a way to avoid losing an entire box hunting for the first hole at 100.
- Shoot a five-round group at 100Same position, same bag, same hold, and let the barrel cool if it is a thin one. Ignore individual shots entirely.
- Measure to the centre of the group, not the middle shotCorrect from the geometric centre of all five. If one shot is obviously yours rather than the rifle's, note it and shoot again rather than discarding it silently.
- Apply the correction and confirm with another fiveThe confirmation group is the zero. If it lands centred, you are done; if not, you have learned that your first group was not representative.
- Record the conditionsTemperature, altitude and the load you used. A zero is only valid for the conditions and ammunition it was shot with.
Why the confirmation group matters
A rifle that groups 1 MOA will scatter individual shots half a minute from centre in any direction on a good day. Correct from a single shot and you are as likely to be chasing your own dispersion as fixing an error. The confirmation group is what separates a zero from a coincidence.
This is also where a cold-bore habit starts paying: if your first round of the day consistently lands away from the group centre, that is a property of the rifle worth knowing, not a fluke. The cold bore drill makes it measurable.
Things that quietly move a zero
- Changing ammunition. A different load has a different muzzle velocity and a different barrel-time, so the zero moves. Re-confirm, do not assume.
- Removing and refitting the scope. Rings rarely return to exactly the same place. Confirm before you trust it.
- A change in season. Powder temperature sensitivity shifts velocity, which shifts impact even at 100 m for some loads.
- Torque on the action screws. Bedding stress changes point of impact on many rifles. A dropped rifle deserves a confirmation group, not optimism.
- A different rest. A bipod on hard concrete and a rear bag on soft ground can move impact measurably on a light rifle.
Telling the app about it
The rifle profile stores the zero distance next to the scope height and the click value. Enter the distance you truly confirmed at, not the one you meant to use. If you zero at 100 m and set the profile to 100 yd, every correction on your card will be slightly wrong in a way that looks plausible — the worst kind of error.
Once the profile is correct, the DOPE card built from it is only as good as this one measurement. It is worth the extra ten rounds.
Frequently asked
Should I zero at 100 metres or 100 yards? +
Whichever your range actually measures. The important thing is that the number in the rifle profile matches reality. Mixing the two introduces a nine per cent distance error at the anchor point of every calculation.
Can I zero at 25 m and be zeroed at 200? +
Approximately, using the near crossing of the trajectory — but the approximation depends on your load and scope height, and a small angular error at 25 m becomes a large one at 200. It is a way to get on paper, not a way to finish.
How often should I re-confirm a zero? +
At the start of any trip that matters, after any change of ammunition, after transport that involved anything harder than a padded case, and whenever a season has passed. It costs five rounds.