How do 20 gauge and .410 bore compare?
A 20-gauge bore measures 0.615 inches; a .410 bore measures 0.410 inches, roughly equivalent to a hypothetical 67 gauge. The wider bore lets the 20 gauge carry more shot: a standard 2-3/4-inch 20-gauge target load holds 7/8 ounce, while a standard 2-1/2-inch .410 target load holds 1/2 ounce. At the same 1,200 fps published velocity, the 20-gauge load therefore puts 1.75 times as much shot in the air, and with it, proportionally more pellets of a given size and more recoil.
| 20 gauge | .410 bore | |
|---|---|---|
| Bore diameter | 0.615" | 0.410" |
| Common shell lengths | 2-3/4", 3" | 2-1/2", 3" |
| SAAMI max pressure | 12,000 psi | 12,500 psi (2-1/2"); 13,500 psi (3") |
| Typical shot payload | 7/8–1-1/8 oz (2-3/4"); up to 1-1/4 oz (3") | 1/2 oz (2-1/2"); up to 3/4 oz (3") |
| Skeet class | 20 gauge | .410 bore |
Current observed shell prices for both appear on the 20 gauge vs .410 bore comparison page.
Why is .410 a "bore" and not a gauge?
Gauge numbers count how many lead balls of the bore's diameter make a pound: twenty 0.615-inch lead balls weigh about a pound, so that bore is 20 gauge. The .410 is instead named by its actual bore diameter in inches. Expressed in the gauge system it would be about 67 gauge. The naming difference is historical; it does not change how either is loaded or fired.
What do published loads show?
The velocities and payloads below are manufacturer-published. Pellet counts are approximate, using nominal lead-shot chart values of about 410 pellets per ounce for #8 shot and about 585 per ounce for #9; individual loads vary.
| Load | Shell | Payload | Shot | Velocity | Approx. pellets |
|---|---|---|---|---|---|
| Winchester AA 20 gauge (AA208) | 2-3/4" | 7/8 oz | #8 | 1,200 fps | ~359 |
| Winchester AA .410 (AA419) | 2-1/2" | 1/2 oz | #9 | 1,200 fps | ~293 |
| Winchester Super-X .410 Heavy Game Load | 3" | 11/16 oz | #4–#6 | 1,135 fps | — |
Two observations from the table:
- Target loads. The .410 AA load uses a smaller shot size (#9) than the 20-gauge AA load (#8). Smaller shot packs more pellets per ounce, which partly offsets the lighter payload: the .410 load carries about 82% as many pellets (293 ÷ 359) with 57% of the payload weight (1/2 ÷ 7/8).
- Game loads. Even the 3-inch .410 game load's 11/16 ounce is less than the 7/8-ounce 2-3/4-inch 20-gauge target load. Moving to the larger shot sizes used on game reduces pellet count further.
Fewer pellets in a pattern of a given size means wider gaps between pellets at a given distance. That arithmetic is the reason the .410 is widely described as requiring closer shots and more precise pointing than larger gauges.
How does recoil compare?
Shotgun recoil comes from the shot charge, the wad, and the powder gas. The part computed here is the momentum of the shot charge alone: payload in grains (1 ounce = 437.5 grains) × velocity (fps) ÷ 225,218, in pound-seconds. Wad weight and powder charge are not published on most boxes and are left out.
| Load | Payload (grains) | Shot momentum |
|---|---|---|
| 20 gauge 7/8 oz at 1,200 fps | 382.8gr | 2.040 lb·s |
| .410 11/16 oz at 1,135 fps | 300.8gr | 1.516 lb·s |
| .410 1/2 oz at 1,200 fps | 218.8gr | 1.166 lb·s |
At the same velocity, momentum scales with payload, so the 20-gauge target load produces 1.75 times the shot momentum of the .410 target load. Gun weight divides that impulse. Because .410 shotguns are often built on small, light frames, the recoil difference a shooter feels between a light .410 and a heavier 20 gauge can be smaller than the payload ratio suggests.
How are patterns measured?
Shot loads are compared by pattern, which is how the pellets spread at a given distance. The standard measure is the percentage of a load's pellets that land inside a 30-inch circle at 40 yards. Pattern percentage depends on the choke (the constriction at the muzzle), the shot size, the hardness of the shot, and the load itself, so two shells in the same gauge can pattern differently in the same gun.
Pattern percentage combines with pellet count to give pattern density. A .410 load and a 20-gauge load that pattern at the same percentage will still put different numbers of pellets in the circle, in proportion to their starting pellet counts. Using the approximate counts above, a 1/2-ounce #9 .410 load patterning at a given percentage would place about 82% as many pellets in the circle as a 7/8-ounce #8 20-gauge load patterning at the same percentage — though the #9 pellets are individually lighter.
Both gauges are offered with interchangeable choke tubes in many modern shotguns, and fixed-choke guns in both gauges are common. Patterning a specific load through a specific gun at a measured distance is the method shooters use to see what that combination does.
Beyond birdshot, both gauges are also loaded with buckshot and slugs. The .410's slug and buckshot payloads are a fraction of the 20 gauge's, in line with the payload ratios shown above.
Which firearms are chambered for each?
Both gauges:
- Pump-action shotguns, including Mossberg 500 models offered in 20 gauge and .410
- Semi-automatic, over-under, side-by-side, and single-shot shotguns from many makers, often in youth or compact configurations
.410 bore only:
- Revolvers built to fire .410 shells and .45 Colt cartridges, such as the Taurus Judge and Smith & Wesson Governor (the Governor also fires .45 ACP with moon clips)
- Lever-action shotguns, such as Henry's .410 lever action
A safety note specific to 20 gauge: a 20-gauge shell can slide past the chamber of a 12-gauge shotgun and lodge in the barrel, where a 12-gauge shell loaded behind it can then be fired into the obstruction. SAAMI's yellow hull color for 20 gauge exists to make the two shells easy to tell apart. Keeping gauges separated is the common practice among owners of both.
What is each gauge commonly used for?
20 gauge is commonly used for:
- Upland birds, doves, and other small game
- Trap, skeet, and sporting clays, including the 20-gauge skeet class
- Turkey hunting with heavy 3-inch loads, and deer hunting with slugs where shotguns are required or allowed
.410 bore is commonly used for:
- The .410 skeet class, one of the four standard skeet gauges alongside 12, 20, and 28
- Small game and pest control at short range
- Revolvers and lever-action shotguns built around the shell
Criteria a reader can apply:
- Typical distance. The pellet-count table shows how much smaller a .410 pattern's pellet budget is; the farther the shot, the more that matters.
- Shooter size and recoil tolerance. The momentum table sets the starting point; gun weight decides the rest.
- Firearm already owned. A .410 revolver or lever action fires only .410 shells (and the revolver's handgun cartridges).
- Clay discipline. Skeet classes are gauge-specific, so the class being shot determines the shell.
How does cost compare?
This article quotes no prices. Per-shell cost depends on production volume and on load type — target loads, game loads, and buckshot or slug loads differ substantially within each gauge. Current observed figures are on the 20 gauge ammo prices and .410 bore ammo prices pages, and the observed trend on 20 gauge price history and .410 bore price history.
Related comparisons
- 12 gauge vs 20 gauge — Payload, recoil, and use cases one step up
- Turkey loads compared — Heavy shotshell characteristics by gauge
Related caliber pages
- 20 gauge ammo prices — Current pricing across tracked retailers
- 20 gauge price history — Observed trend over time
- .410 bore ammo prices — Current pricing across tracked retailers
- .410 bore price history — Observed trend over time
Sources
- SAAMI Cartridge & Chamber Drawings — Shotshell dimensions, maximum average pressure, and hull color convention
- Winchester Ammunition — AA208, AA419, and Super-X .410 Heavy Game Load published payload and velocity
- National Skeet Shooting Association — Skeet gauge classes (12, 20, 28, .410)