How are shotgun shot sizes numbered?
In the US system, a smaller shot number means a larger pellet. Birdshot runs from #9 (about 0.08 inch) up through #2 and #1 to BB (0.18 inch). Buckshot uses a separate scale that runs from #4 buck (about 0.24 inch) up through #1 buck, 0 buck and 00 ("double-aught") buck to 000 buck (about 0.36 inch). The two scales overlap in name but not in size: #4 birdshot is 0.13 inch, while #4 buckshot is 0.24 inch.
For numbered US birdshot there is a simple rule: subtract the shot number from 17 to get the diameter in hundredths of an inch. #8 shot is 17 − 8 = 9, so 0.09 inch; #4 shot is 17 − 4 = 13, so 0.13 inch. The rule does not apply to buckshot.
Pellet size drives everything else in a shotshell. For a fixed payload weight, smaller pellets mean many more pellets and a denser pattern, but each pellet carries less energy and penetrates less. Larger pellets mean fewer projectiles, each of which carries more energy.
What are the birdshot sizes?
Nominal diameters and approximate pellet counts per ounce of lead shot, from standard US shot-size tables:
| US shot size | Diameter (in.) | Diameter (mm) | Lead pellets per ounce |
|---|---|---|---|
| #9 | 0.080 | 2.03 | about 585 |
| #8½ | 0.085 | 2.16 | about 497 |
| #8 | 0.090 | 2.29 | about 410 |
| #7½ | 0.095 | 2.41 | about 350 |
| #7 | 0.100 | 2.54 | about 291 |
| #6 | 0.110 | 2.79 | about 225 |
| #5 | 0.120 | 3.05 | about 170 |
| #4 | 0.130 | 3.30 | about 135 |
| #3 | 0.140 | 3.56 | about 108 |
| #2 | 0.150 | 3.81 | about 87 |
| #1 | 0.160 | 4.06 | about 72 |
| BB | 0.180 | 4.57 | about 50 |
Sizes larger than BB (BBB, T, F and others) exist, mainly in steel shot for waterfowl. European, British and Australian systems use different numbering, so a "#6" made to a European standard is not exactly the same diameter as a US #6.
Steel and other non-toxic shot. Steel is less dense than lead, so a steel pellet of the same diameter weighs less, there are more of them per ounce, and each one carries less energy at a given distance. A common rule of thumb is to move up about two shot sizes when switching from lead to steel. In the US, federal regulations have required non-toxic shot for waterfowl hunting nationwide since 1991; steel, bismuth and several tungsten-based materials are approved. Turkey loads compared covers how dense tungsten shot (TSS) changes the size-versus-energy trade-off.
What are the buckshot sizes?
| Buckshot size | Diameter (in.) | Diameter (mm) | Lead pellets per ounce |
|---|---|---|---|
| #4 buck | 0.24 | 6.10 | about 21 |
| #3 buck | 0.25 | 6.35 | about 18 |
| #2 buck | 0.27 | 6.86 | about 14 |
| #1 buck | 0.30 | 7.62 | about 11 |
| 0 buck | 0.32 | 8.13 | about 9 |
| 00 buck | 0.33 | 8.38 | about 8 |
| 000 buck | 0.36 | 9.14 | about 6 |
Buckshot pellets are large enough that they are stacked into the shell in layers rather than poured, which is why manufacturers list buckshot loads by pellet count rather than by payload weight. Many buckshot loads also pack a granulated plastic buffer between the pellets to reduce deformation when the shell is fired.
How many pellets are in a standard shotgun load?
Published pellet counts for one widely distributed line (Federal Power-Shok buckshot) and two other Federal loads show how gauge, shell length and pellet size interact:
| Gauge | Shell length | Shot size | Pellets | Published velocity |
|---|---|---|---|---|
| 12 | 2¾-inch | 000 buck | 8 | 1,325 fps |
| 12 | 2¾-inch | 00 buck | 9 | 1,325 fps |
| 12 | 2¾-inch | #1 buck | 16 | 1,325 fps |
| 12 | 2¾-inch | #4 buck | 27 | 1,325 fps |
| 12 | 3-inch | 00 buck | 15 | 1,210 fps |
| 12 | 3-inch | #4 buck | 41 | 1,210 fps |
| 12 | 3½-inch | 00 buck | 18 | 1,100 fps |
| 20 | 2¾-inch | #3 buck | 20 | 1,200 fps |
| .410 | 2½-inch | 000 buck | 4 | 850 fps |
Other manufacturers load different counts in the same shell — 12 gauge 00 buck loads range from 8 to 18 pellets depending on shell length and design — so the pellet count printed on a specific box is the figure that applies. Reduced-recoil versions usually trade some velocity for lower recoil.
Birdshot is sold by payload weight instead. Federal's Top Gun target line lists 1⅛ ounces for 12 gauge 2¾-inch, ⅞ ounce for 20 gauge 2¾-inch, ¾ ounce for 28 gauge and ½ ounce for .410 2½-inch shells. Multiplying payload weight by pellets per ounce gives an approximate count, for example:
| Load | Approximate pellets (computed) |
|---|---|
| 12 gauge, 1⅛ oz of #8 | about 460 |
| 12 gauge, 1⅛ oz of #7½ | about 395 |
| 20 gauge, ⅞ oz of #8 | about 360 |
| .410, ½ oz of #9 | about 290 |
These are arithmetic from nominal values, not counts from a specific box; actual pellet counts vary with the shot alloy and the manufacturer's tolerances.
What do gauge and bore mean?
Gauge is an old unit based on lead balls. A shotgun's gauge is the number of lead balls, each exactly the diameter of the bore, that together weigh one pound. Twelve balls that fit a 12 gauge bore weigh a pound; twenty smaller balls that fit a 20 gauge bore weigh a pound. That is why a larger gauge number means a smaller bore.
| Designation | Nominal bore diameter |
|---|---|
| 12 gauge | 0.729 in. (18.5 mm) |
| 20 gauge | 0.615 in. (15.6 mm) |
| 28 gauge | 0.545 in. (13.8 mm) |
| .410 bore | 0.410 in. (10.4 mm) |
The .410 bore is the exception to the system: it is named for its bore diameter in inches, not its gauge. A larger bore holds a larger payload at a given pressure, which is why a 12 gauge shell carries more shot than a 20 gauge or .410 shell of the same length. For a load-by-load comparison of the two most common gauges, see 12 gauge vs 20 gauge.
What does shell length mean?
Shell length — 2½, 2¾, 3 or 3½ inches — is the length of the hull after firing, with the crimp at the front unfolded. An unfired shell is shorter than its label. Longer shells hold more shot or more powder, or both, and usually produce more recoil.
Every shotgun barrel is marked with its chamber length. A shell longer than the chamber does not have room to unfold fully, which can raise pressure; that is why shell length is printed on every box, to be matched against the barrel marking. Shells shorter than the marked chamber length are generally compatible, although some semi-automatic shotguns are designed to cycle only within a certain range of loads; the firearm's manual lists what it accepts.
What are slugs, and how do they differ from shot?
A slug is a single projectile in place of a shot charge. Federal's Power-Shok rifled slugs illustrate standard weights: 1 ounce in 12 gauge 2¾-inch, 1¼ ounces in 12 gauge 3-inch, ¾ ounce in 20 gauge and ¼ ounce in .410.
Two main families exist:
- Rifled (Foster-type) slugs have external ribs and a hollow base, and are designed to be fired from smooth-bore barrels.
- Sabot slugs are smaller-diameter projectiles held in a plastic sleeve, designed for rifled shotgun barrels, where the spin stabilizes them.
A slug penetrates far more material than buckshot or birdshot. 12 gauge home defense loads compared covers how slugs, buckshot sizes and birdshot differ in penetration and wall penetration.
How are shot sizes used?
Shot size is matched to the target's size and distance. The pairings below are the typical uses that manufacturers' product lines are designed around, not requirements:
| Shot size range | Typical designed-for use |
|---|---|
| #9, #8, #7½ | Clay targets (skeet, trap, sporting clays) and small upland birds such as doves and quail |
| #6, #5, #4 | Larger upland birds, rabbits and squirrels; heavier turkey loads |
| #2, #1, BB (often steel) | Waterfowl, especially geese |
| #4 buck to 000 buck | Deer and hogs where buckshot is legal, and defensive loads |
| Slugs | Deer in areas that restrict rifles, and longer-distance shotgun use |
Game regulations often set minimum or maximum shot sizes, require non-toxic shot, or restrict buckshot and slugs for particular species and areas, so the state regulations govern what is legal for a given hunt.
How can you compare shotgun ammunition prices?
Shotshell prices vary with gauge, payload, shot material and pellet type, so this page does not freeze a figure. Tracked prices and history are on the gauge pages, including 12 gauge buckshot and 12 gauge slugs.
Related articles
- 12 gauge home defense loads compared
- Turkey loads compared
- 12 gauge vs 20 gauge
- Rimfire vs centerfire
Sources
- Shotgun cartridge — Wikipedia — US birdshot and buckshot size tables, the 17-minus rule, gauge definition and bore diameters
- Federal Power-Shok Buckshot — Published pellet counts and velocities (F127 000, F127 00, F127 1B, F127 4B, F131 00, F131 4B, F203 3B)
- Federal Premium Buckshot 12 ga 3½-inch 00 (P135F 00) — 18-pellet load
- Federal Personal Defense .410 000 Buck (PD412JGE 000) — 4-pellet .410 load
- Federal Top Gun — Birdshot payload weights by gauge
- Federal Power-Shok Rifled Slug — Slug weights by gauge
- U.S. Fish and Wildlife Service — Nontoxic shot regulations — Waterfowl non-toxic shot requirement