Birdshot
Many smaller pellets form a pattern. In the U.S. size examples below, a higher birdshot number means a smaller pellet. Lead, steel, bismuth, and tungsten-based products of the same numbered size need not have the same mass or behavior.
THE CARTRIDGE LIBRARY · SHOTSHELL
.410 bore
A bore-diameter designation rather than a conventional gauge number. The cartridge family includes birdshot, specialty shot loads, and slugs with different application limits.
2A Ledger reference desk · Sources checked October 18, 2026
Read the dimensions
- Folded length · max
- 2.360 in
59.944 mm - Nominal shell class
- 2½ in
63.500 mm - Bore diameter · min
- 0.410 in
10.414 mm - Rim diameter · max
- 0.535 in
13.589 mm
Know the exact name
At a glance
- Cartridge family
- Shotshell
- Bore specification
- 0.4100 in / 10.414 mmBore minimum
- Factory examples
- 4 shot loadsSelected catalog examples
- Weight in cited examples
- Ounces / pellet countPayload is separate from gauge
.410 bore is identified by its complete cartridge designation. The resource-table alternative is 410 Bore. A caliber number, bullet diameter, or family resemblance on its own does not identify ammunition compatibility.
.410 is not 410 gauge. Shell length, firearm type, and load restrictions still have to match the firearm's manual.
Dimensions: open the exact dimensional drawing ↗. The displayed number is bore minimum, rather than an assertion that every manufactured projectile or barrel has this exact diameter.
Origins & evolution
Background & development
The .410 has long been associated with small sporting shotguns, but its American history includes more than introductory single-shots. Winchester’s 1920 Model 20 appeared in a Junior Trap Shooting Outfit, linking the bore to an organized small-gun sporting market. The Model 42 pump, introduced in 1933, later gave it a particularly well-known repeating-shotgun platform.
Competitive skeet helped preserve another identity for the .410: a demanding small-bore event rather than simply a beginner’s gun. NSSA championship programs continue to place it beside the 12-, 20- and 28-gauge events. Its limited shot charge makes that sporting tradition quite different from the impression created by the small gun’s easy handling. The name itself also records a different measurement convention: .410 describes nominal bore diameter in inches, while the gauge-number system used for the other common shotgun sizes works differently. That distinction has accompanied a long and varied sporting life.
Historical sources: Winchester: Model 20 Junior Outfit and 1933 Model 42 history ↗ · NSSA: .410-bore World Skeet event ↗ · Federal: bore and gauge terminology ↗
Construction changes the story
Loads, variations & specialty offerings
Gauge identifies the bore family. Shot number identifies the approximate diameter of an individual pellet. Ounces describe the combined shot payload, while a buckshot product may specify a pellet count. Shell length is a separate chamber-fit specification, normally referenced to the fired shell.
Buckshot
Fewer, larger pellets are commonly listed by size and pellet count. #4 birdshot and #4 buckshot have very different diameters. Pattern behavior depends on the exact load, firearm, and choke; there is no universal inches-per-yard rule.
Slugs
A slug is a single projectile. Rifled/Foster-type and sabot designs have different barrel recommendations. Federal identifies sabot loads for rifled barrels; follow the exact ammunition and barrel maker’s instructions.
Materials & specialty loads
Lead & bismuth
Lead remains common in target and upland loads where permitted. Bismuth is an alternative material offered in selected sporting loads; compare the maker’s product specification and shotgun/choke compatibility.
Steel
Steel shot has different density and hardness from lead. A shot-size label alone does not reproduce the same pellet mass. Use ammunition approved for the barrel and choke; check current local hunting requirements separately.
Tungsten-based & specialty
TSS and other tungsten-based products can use small pellets and dense payloads. The exact alloy and construction matter. Mixed-shot, reduced-recoil, short-shell, and handgun-marketed products retain their own firearm restrictions.
Compare pellet sizes visually
The two circles use the same screen scale to compare nominal pellet diameter. They are not life-size, do not represent a shot pattern, and do not show an individual load’s pellet count.
See nominal pellet sizes in inches and millimeters
| Pellet | Inches | Millimeters |
|---|---|---|
| #9 birdshot | 0.08 | 2.032 |
| #8 birdshot | 0.09 | 2.286 |
| #7½ birdshot | 0.095 | 2.413 |
| #6 birdshot | 0.11 | 2.794 |
| #5 birdshot | 0.12 | 3.048 |
| #4 birdshot | 0.13 | 3.302 |
| #3 birdshot | 0.14 | 3.556 |
| #2 birdshot | 0.15 | 3.810 |
| #1 birdshot | 0.16 | 4.064 |
| BB birdshot | 0.18 | 4.572 |
| BBB birdshot | 0.19 | 4.826 |
| T birdshot | 0.2 | 5.080 |
| #4 buckshot | 0.24 | 6.096 |
| #3 buckshot | 0.25 | 6.350 |
| #2 buckshot | 0.27 | 6.858 |
| #1 buckshot | 0.3 | 7.620 |
| 00 buckshot | 0.33 | 8.382 |
| 000 buckshot | 0.36 | 9.144 |
Federal: shotshell components and nominal shot sizes ↗
Factory shot-load examples
| Product code | Load family | Shell length (in) | Payload | Shot size | Muzzle velocity |
|---|---|---|---|---|---|
| H412 | Lead birdshot | 2½ | ½ oz | 6, 7½ | 1,200 fps 366 m/s |
| WF413 | Steel birdshot | 3 | ⅜ oz | 6 | 1,400 fps 427 m/s |
| PTSS419F | Tungsten-based specialty birdshot | 3 | 13/16 oz | 7, 9 | 1,100 fps 335 m/s |
| PD412JGE000 | Handgun-marketed buckshot | 2½ | 4 pellets | 000 | 850 fps 259 m/s |
The cited .410 handgun-marketed buckshot product has different test conditions from a sporting shotgun. Its 850 fps catalog figure must not be treated as a universal .410 shotgun velocity.
Explore the published data
Ballistics you can inspect
Shotshell muzzle velocity, pellet patterns, and slug trajectories answer different questions. Birdshot and buckshot cannot be represented as a single bullet curve: individual pellet drag and pattern behavior require a load-specific test. The pellet comparison above shows size, not performance.
Select a legend entry to add or remove its line. Hover or tap a plotted point, or use the position slider. With the graph focused, arrow keys move the inspector. Solid dots identify source points; dashed connectors show estimates between them. Load construction, pressure category, and test setup can differ even at the same grain weight.
Read the original values as accessible tables
.410 bore: factory velocity downrange
| Exact load | Source | Published points |
|---|---|---|
| 109 gr Federal 2½-inch rifled hollow-point slug | Federal | 0: 1775; 25: 1540; 50: 1340; 75: 1180; 100: 1060; 125: 980 |
Source records for plotted slugs
| Maker / product | Bullet mass | Published construction | Muzzle velocity | Test barrel | Source |
|---|---|---|---|---|---|
| FederalF412 RS | 109 gr 7.06 g | 2½-inch rifled hollow-point slug | 1,775 fps 541 m/s | 26 in | Federal · PDF p. 63 ↗ |
Direct answers
Common questions
What is .410 bore?
A bore-diameter designation rather than a conventional gauge number. The cartridge family includes birdshot, specialty shot loads, and slugs with different application limits.
Is .410 bore a shot size?
Gauge or bore identifies the shell and bore family. Birdshot and buckshot size labels describe individual pellets. The load also needs a payload, shell length, material, and exact product identification.
Are similarly named cartridges interchangeable?
.410 is not 410 gauge. Shell length, firearm type, and load restrictions still have to match the firearm's manual.
Are the graph values measured or estimated?
The downrange view uses the exact manufacturer catalog records shown in the source table. Dashed connectors and intermediate inspector values use linear interpolation between the displayed source points. Calculated energy uses the listed bullet mass and velocity.
Does higher energy mean the best load?
Energy is calculated from mass and velocity. It does not establish accuracy, expansion, penetration, pattern density, recoil, or suitability for a particular firearm. Use the exact product documentation and firearm manual.
Trace the facts
Sources & methodology
Compiled by 2A Ledger from the linked standards, manufacturer publications, and identified test records. Checked October 18, 2026. Historical tests and older catalogs retain their original dates; a listing here does not establish current availability.
- SAAMI: dimensional drawing · PDF p. 39 ↗
- Federal: shotshell components and nominal shot sizes ↗
- Federal: 2026 ammunition catalog ↗
- Federal · PDF p. 63 ↗
- Winchester: Model 20 Junior Outfit and 1933 Model 42 history ↗
- NSSA: .410-bore World Skeet event ↗
Diameter figures preserve the cited drawing convention. Inch–millimeter conversion uses exactly 25.4 mm per inch. Factory specifications describe the maker’s test setup; your firearm, ammunition lot, temperature, and measuring method can produce different results. This is an educational factory-ammunition reference, not a reloading manual.