Temperature, Atmosphere & Ballistic Performance
Why real hunting conditions matter more than box velocity.
Why Weather Changes Ballistic Reality
A shotshell does not perform in a vacuum.
It performs in cold air, humid air, dense air — often late in the season.
Yet most expectations are built around fixed distances and published velocities, without considering how environmental conditions quietly erode performance.
The result is familiar to many hunters:
- loads that felt decisive early in the season
- become inconsistent later on
- even when distance and shot placement appear unchanged
This page explains why that happens.
Important note on interpretation
Weather conditions modify pellet velocity and penetration, but the interpretation framework remains unchanged.
Ethical range limits are still defined by the combined effects of penetration and pattern density.
Reference Conditions Used in the Database
All ballistic data published on Waterfowl Ballistics is calculated using the same reference environment, in order to allow meaningful comparisons across species, pellet sizes, and materials.
Standard reference conditions:
- Temperature: 41 °F
- Atmospheric pressure: 1015 hPa
- Relative humidity: 80%
- Muzzle velocity reference: measured at 68 °F ammunition temperature
These values represent a realistic, neutral baseline, not ideal laboratory conditions.
However, real-world waterfowl hunting in North America often departs significantly from this baseline — sometimes by a wide margin.
Why Environmental Conditions Matter
External ballistics are governed primarily by air density.
Air density is influenced by:
- ambient temperature
- atmospheric pressure
- humidity
Denser air increases drag.
Increased drag reduces retained velocity, and therefore penetration.
Cold, high-pressure conditions — typical of late-season hunts — consistently reduce terminal performance, even when distance and load remain unchanged.
But external ballistics are only half of the story.
Ammunition Temperature: The Overlooked Variable
In addition to air density, ammunition temperature directly affects muzzle velocity.
Cold shells produce lower velocities due to reduced powder efficiency.
This is an internal ballistic effect, and it compounds the external effects of dense air.
For practical field modeling, the database assumes a simple linear approximation:
Approximately 1.8 fps per °F of muzzle velocity change, relative to a 68 °F ammunition temperature reference.
This is not a powder-specific laboratory constant.
It is a conservative, field-usable approximation for real hunting scenarios.
All penetration values shown below therefore include:
- atmospheric effects (air density)
- velocity loss or gain due to ammunition temperature
Four Common U.S. Hunting Scenarios
| Scenario | Typical context |
|---|---|
| 65 °F / 1018 hPa / 80% | Early season, Southern states (Louisiana, Texas) |
| 41 °F / 1025 hPa / 60% | Mid-season Midwest (Illinois, Missouri) |
| 23 °F / 1030 hPa / 90% | Cold, humid winter hunts |
| 14 °F / 1035 hPa / 50% | Late season Northern states (Dakotas, Great Lakes) |
These conditions reflect actual field environments, not extreme edge cases.
Penetration Comparison — Constant Nominal Load
Baseline load used for the comparisons below: 12 gauge, 3″, 1 1/4 oz, 1550 fps (nominal), with muzzle velocity referenced to 68 °F ammunition temperature.
| Pellet | 65 °F | 41 °F | 23 °F | 14 °F |
|---|---|---|---|---|
| BB | 2.62 in | 2.51 in | 2.48 in | 2.46 in |
| #2 | 1.96 in | 1.86 in | 1.83 in | 1.82 in |
| #4 | 1.56 in | 1.46 in | 1.44 in | 1.42 in |
At a glance, the numbers may appear close.
In practice, the margin loss is significant.
Practical Example — Mallard Hunting Implications
A penetration value around 1.56 inches, as observed for steel #4 in warm early-season conditions, is fully adequate for mallard hunting at 40 yards.
Vital organs are reliably reached, and lethality margins are comfortable.
Under late-season conditions, however:
- colder air
- higher pressure
- colder ammunition
penetration for the same load drops toward 1.42–1.44 inches.
At that point, the load approaches the ethical limit for mallards.
This leaves little margin for:
- angled shots
- feather compression
- bone contact
A load that is clearly ethical in September can become borderline in December — without changing distance or pellet size.
What This Means in the Field
Distance did not change.
Shot size did not change.
The load did not change.
The margin did.
This effect is even more critical for geese, where penetration requirements are substantially higher and margins are already thin.
Ballistics are not fixed numbers — they are situational realities.
Maximum Ethical Distance — Real Hunting Conditions
The following data quantifies how real atmospheric conditions reduce maximum ethical shooting distance, without changing pellet size or shot material.
Reference Load Used for All Calculations
All distances shown in the tables below are calculated using the same baseline load:
- Gauge: 12 gauge
- Shell length: 3″
- Payload: 1 1/4 oz
- Nominal muzzle velocity: 1550 fps
- Velocity reference: measured at 68 °F ammunition temperature
This represents a common, high-performance waterfowl load widely used in North America.
Distances shown assume this specific baseline. Lighter payloads, shorter shells, or lower velocities will reduce ethical distance further.
How to Read These Tables
- Distances shown are maximum ethical distances (yards)
- Assumes centered vital hit
- No allowance for:
- shot angle
- bone impact
- feather compression
- range estimation error
Margin disappears before failure.
These distances indicate where certainty ends — not where pellets suddenly stop working.
Scenario 1 — Early Season / Favorable Conditions
Mild temperature, moderate pressure, warm ammunition
| Pellet | Mallard (yd) | Teal (yd) | Canada Goose (yd) |
|---|---|---|---|
| BB | — | — | 60 |
| B | 38 | — | 50 |
| #1 | 49 | — | 35 |
| #2 | 59 | — | 25 |
| #3 | 59 | 45 | — |
| #4 | 46 | 55 | — |
| #5 | 34 | 61 | — |
| #6 | 24 | 48 | — |
| #7 | — | 36 | — |
| #8 | — | 25 | — |
Scenario 2 — Mid-Season / Typical Conditions
Cooler temperatures, higher pressure
Scenario 3 — Cold & Humid Winter Conditions
Dense air, cold ammunition
Scenario 4 — Late Season / Cold & High Pressure
Cold, dry air — Northern states
Summary — Ethical Distance Loss Across Weather Scenarios
Same load. Same pellet. Same distance estimation.
Only weather changes.
Non-member preview: mid-season typically costs several yards of margin. In winter conditions, the loss can approach 10 yards depending on species and pellet size.
What This Means in Practice
- Ethical distance does not collapse suddenly
- It erodes quietly, yard by yard
- Weather removes margin before distance feels long
Key Takeaway
- Weather alone can remove up to 10 yards of ethical range
- No change in shell, pellet size, or shooting habits
- Only atmospheric conditions
Distance did not change.
Your margin did.
Important Notes
- These distances are not recommendations
- They represent upper ethical limits
- Real-world shooting requires additional margin
- Slower loads or lighter payloads will reduce distances further