# Zero shift with temperature: why your point of impact drifts > Cold ammunition and dense cold air both slow your bullet, so a zero confirmed on a warm day will land lower on a cold one. Re-check with sighting shots whenever the temperature swings, and log the clicks you add back. - Canonical URL: https://target-log.net/blog/zero-shift-temperature/ - Published: 2026-11-02 (updated 2026-11-02) - Category: Gear & equipment - Tags: zeroing, 50m rifle, intermediate - Read time: ~6 min ## Key takeaways - Temperature moves your point of impact through two mechanisms: colder ammunition leaves the barrel slower, and colder air drags the bullet more. - Both effects push the same direction, so a cold morning shoots lower than a warm afternoon at the same sight setting. - At 50m the shift is small but ring-relevant, which is what sighting shots are for. - Store and carry your ammunition at outdoor ambient temperature so it behaves like it did when you zeroed. You did everything right. Same position, same ammunition, same [sight picture](/blog/sight-alignment-and-sight-picture-for-10m-air-rifle/) you used to zero last month. Yet the group sits a ring low, and every shot you add only confirms it. If this has happened to you on the first cold morning of the season, you have met the temperature zero shift: a point of impact that moves with the thermometer rather than with anything you are doing wrong. Outdoor shooters at 50m and 300m live with it constantly, and once you understand it, the fix is mostly patience and bookkeeping. ## Does temperature really shift your zero? Yes. Two separate physical effects both slow the bullet when it gets colder, so the point of impact drops as temperatures fall and rises as they climb. Colder ammunition ignites and burns slightly less energetically, which costs muzzle velocity, and colder air is denser, which drags on the bullet over its flight. A zero confirmed on a warm afternoon can genuinely print lower on a frosty morning. Neither effect involves your sights moving. Your diopter has not slipped and your position has not changed. The bullet simply arrives at the target on a slightly different arc, and at 50m that difference is measured in the same units as your scoring rings. If you have already worked through [how to zero your air rifle diopter sights](/blog/how-to-zero-your-issf-air-rifle-diopter-sights/), you may have noticed this in your own records: a click or two of drift between sessions that correlates with the weather rather than with anything you changed. ## Why does cold ammunition shoot slower? Rimfire ammunition is the classic case. The priming compound and powder in a .22 LR round are temperature sensitive, and independent shooters who have chronographed match lots across temperature ranges consistently report muzzle velocity changing by somewhere around 0.4 to 0.8 feet per second per degree Fahrenheit. Call it roughly half a foot per second. A thirty-degree drop then costs you something like fifteen feet per second at the muzzle, before air density does anything at all. Fifteen feet per second sounds trivial, and over most distances it is. But match .22 LR runs close to the speed of sound on purpose, staying subsonic so the bullet never wobbles through the transonic zone. Anything that nudges velocity, in either direction, moves the bullet away from the point where your barrel and that lot shoot their tightest groups. This is one more reason to buy ammunition that is genuinely subsonic to begin with, and to keep it stored consistently between matches. The practical version of this is simple. The ammunition you fire on match day should be at the same temperature it was at when you confirmed your zero. A box that spent the drive to the range on the heated dashboard behaves differently from one that rode in the boot. ## Why does air temperature add to the problem? Cold air is denser air. More molecules per cubic metre means more drag on the bullet for every metre it travels, so the bullet sheds velocity faster and drops further before it reaches 50m. Warm air thins out, drag falls, the trajectory flattens, and the same sight setting now prints higher. Notice that the two effects stack in the same direction. A cold day gives you slower ammunition at the muzzle and thicker air to push through afterwards. That is why a hard seasonal change moves the group more than a mild morning-to-afternoon swing, and why shooters who only train in one season get surprised twice a year. This is also why the drift shows up outdoors and not in your indoor league. Ten-metre air gun events happen in a hall where the temperature barely moves, so temperature-driven zero shift never really arises for air rifle and air pistol shooters. Take the same discipline out to 50m smallbore or 300m full-bore and the weather becomes part of the course of fire, just like the wind. ## How big is the shift at actual match distance? Small, but scoring-relevant. Nobody sensible will hand you a universal number of millimetres, because it depends on your lot, your barrel, and the size of the temperature swing. What the whole smallbore community agrees on is the shape of it: a group that moves vertically, drops in the cold, rises in the heat, and stays tight while it does so. That is actually the diagnostic that separates zero shift from a technique problem. A position fault opens the group or drags it sideways. Temperature moves a tight group bodily up or down the target. When you see a neat cluster sitting a ring low, do not rebuild your position; check the thermometer, then shoot [your sighting shots](/blog/issf-sighting-shots/) before you touch a single click. Logging groups with a [shot group analyzer](/shot-group-analyzer/) makes this obvious within a season, because you can plot group centre against date and watch it track the weather. If you already keep a diary for reading conditions, add a temperature column and the pattern will find you. ## How do you manage zero shift on match day? Treat the zero as conditional, not permanent. These habits cover most of it: 1. **Zero in season, not once a year.** Confirm your zero when the temperature band changes, not after every cold snap. Twice a season covers most climates. 2. **Let ammunition acclimatise.** Get the box to range temperature before the prep period ends. Not heated, not frozen: ambient. 3. **Use sighters as verification, not discovery.** Two or three sighting shots tell you whether today needs that click you already suspected. Shoot them properly, in your normal rhythm, instead of rushing to the match card. 4. **Write down the correction.** "Plus two clicks down, 8 degrees, north end" is a note that pays for itself all winter. Next cold match, you start from evidence instead of guesswork. 5. **Do not over-correct from one shot.** A single low sighting shot might be the shooter, not the air. Confirm with a pair before you move the sight. Shooters who also compete in genuinely cold conditions should pair this with the right [clothing for cold outdoor ranges](/blog/cold-weather-shooting-clothing-outdoor-ranges/), because shivering costs more score than ballistics ever will. ## Is it the temperature, or is it me? Honest answer: check the group first, the weather second, yourself third. A tight group in the wrong place is almost always conditions or zero. An open group anywhere is usually the shooter, the position, or tired ammunition handling. Temperature drift is the explanation that fits the first picture, and once you start logging it, you will stop spending sighters chasing a problem that two clicks and a jumper would have solved. The wind still deserves most of your respect outdoors; if you have not yet built a routine for it, start with [reading wind flags, mirage and hold-offs at 50m](/blog/reading-wind-for-50m-rifle-flags-mirage-and-hold-offs/). Temperature is the quieter half of the same subject, and it rewards the same thing: notes, patience, and a healthy suspicion of anything you have not confirmed with a sighting shot. ## faq **Should I zero in the morning or afternoon of a match?** Use the prep and sighting period on the day, in the conditions of the day. A zero carried over from a different temperature band is a starting point, never a guarantee. **Does altitude do the same thing?** It works through the same channel, air density, and thinner air at altitude prints higher just like warm air does. For most shooters altitude changes slowly enough that it hides inside a normal re-zero, while temperature can swing within a single match. **Does this apply to 300m rifle?** Yes, and more so, because every ballistic effect scales with distance. Full-bore shooters see temperature and air density in their elevation settings as a matter of routine. ## FAQ **Q: How much does temperature change point of impact at 50m?** A: Enough to matter for score, not enough to miss the target. Community testing on .22 LR match ammunition reports muzzle velocity changing by roughly half a foot per second per degree Fahrenheit, so a big seasonal swing moves the group by a ring or so at 50m. Confirm with sighting shots rather than trusting a fixed correction. **Q: Do I need to re-zero every time the weather changes?** A: No. Re-zero when the season changes or after a swing of many degrees, and use your sighting shots on match day to confirm and fine-tune. Chasing the zero on every cold morning usually adds error instead of removing it. **Q: Does temperature affect air rifles and air pistols?** A: Barely, in ISSF context, because 10m air gun events are shot indoors in stable conditions. Gas guns are a different story outdoors: CO2 pressure is strongly temperature dependent. PCP rifles hold their velocity far better across a normal day. **Q: Should I keep my ammunition warm in winter?** A: Keep it at whatever temperature you will shoot in. Ammunition pulled from a warm car and fired into cold air gives you one velocity at the muzzle and different behaviour by the time you re-zero. Let it sit at range temperature, then confirm with sighters. --- Part of the [TargetLog blog](https://target-log.net/blog/). Site index for AI/LLM agents: https://target-log.net/llms.txt ยท all articles: https://target-log.net/llms-full.txt.