The 20 Gauge is a shotshell standardised by SAAMI in ANSI/SAAMI Z299.2, which lists it in 2 3/4 and 3 inch shells, at a maximum average pressure of 12,000 psi in each. This guide sets out SAAMI’s published reference velocity for each shot weight in each shell length, for lead and non-lead shot, then its slug and buckshot reference loads, and compares the 20 Gauge with the 410 Bore on the same basis.
20 Gauge ballistics chart: SAAMI reference data
SAAMI lists shotshell reference loads by shot weight within each shell length, and publishes a nominal mean instrumental velocity for each, measured at 3 feet from the standard test barrel. Rifle and handgun cartridges are measured at 15 feet, so a shotshell velocity is not measured on the same basis as theirs. SAAMI lists lead shot and non-lead shot loads separately and fires them in test barrels with different chokes, so the tables give them in separate columns. SAAMI publishes no energy for shot loads, so no energy is shown.
20 Gauge, 2 3/4 inch shell
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| Shot weight | Lead shot: velocity at 3 ft | Non-lead shot: velocity at 3 ft |
|---|---|---|
| 3/4 oz | 1,390 fps | 1,300; 1,425 fps |
| 22 gm | 1,275 fps | Not listed |
| 7/8 oz | 980; 1,135; 1,210; 1,300; 1,350 fps | 1,210 fps |
| 1 oz | 1,165; 1,220; 1,300; 1,350 fps | 1,135; 1,350 fps |
| 1 1/8 oz | 1,175 fps | 1,100 fps |
20 Gauge, 3 inch shell
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| Shot weight | Lead shot: velocity at 3 ft | Non-lead shot: velocity at 3 ft |
|---|---|---|
| 7/8 oz | Not listed | 1,200; 1,300; 1,500; 1,600 fps |
| 1 oz | Not listed | 1,330 fps |
| 1 1/16 oz | Not listed | 1,250; 1,350 fps |
| 1 1/8 oz | 1,285 fps | 1,225; 1,300 fps |
| 1 3/16 oz | 1,295 fps | Not listed |
| 1 1/4 oz | 1,185; 1,300 fps | 1,175; 1,225 fps |
| 1 7/16 oz | 1,100 fps | Not listed |
20 Gauge slug ballistics: SAAMI reference data
SAAMI lists slug loads separately from shot loads, and for slugs it publishes velocity at both 3 feet and 15 feet from the test barrel. A slug is a single projectile, so its energy can be computed from its weight as grains × fps² ÷ 450,437, taking 1 ounce as 437.5 grains. SAAMI’s slug weights are nominal, so the computed energy is nominal too, and it is energy at the test barrel, not downrange.
20 Gauge rifled slugs
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| Shell length, slug weight | Velocity at 3 ft / computed energy | Velocity at 15 ft / computed energy |
|---|---|---|
| 2 3/4 inch, 1/2 oz | 1,810 fps / 1,591 ft-lb | 1,770 fps / 1,521 ft-lb |
| 2 3/4 inch, 5/8 oz | 1,570 fps / 1,496 ft-lb | 1,540 fps / 1,440 ft-lb |
| 2 3/4 inch, 3/4 oz | 1,570 fps / 1,796 ft-lb | 1,540 fps / 1,728 ft-lb |
| 2 3/4 inch, 7/8 oz | 1,540 fps / 2,016 ft-lb | 1,505 fps / 1,925 ft-lb |
| 3 inch, 3/4 oz | 1,800 fps / 2,360 ft-lb | 1,755 fps / 2,244 ft-lb |
20 Gauge saboted slugs
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| Shell length, slug weight | Velocity at 3 ft / computed energy | Velocity at 15 ft / computed energy |
|---|---|---|
| 2 3/4 inch, 250 gr | 1,790 fps / 1,778 ft-lb | 1,775 fps / 1,749 ft-lb |
| 2 3/4 inch, 260 gr | 1,700 fps / 1,668 ft-lb | Not established |
| 2 3/4 inch, 260 gr | 1,795 fps / 1,860 ft-lb | 1,780 fps / 1,829 ft-lb |
| 2 3/4 inch, 260 gr | 1,850 fps / 1,976 ft-lb | 1,835 fps / 1,944 ft-lb |
| 2 3/4 inch, 260 gr | 1,900 fps / 2,084 ft-lb | Not established |
| 2 3/4 inch, 5/8 oz | 1,400 fps / 1,190 ft-lb | Not established |
| 2 3/4 inch, 5/8 oz | 1,500 fps / 1,366 ft-lb | Not established |
| 2 3/4 inch, 5/8 oz | 1,600 fps / 1,554 ft-lb | Not established |
| 2 3/4 inch, 7/8 oz | 1,270 fps / 1,371 ft-lb | 1,250 fps / 1,328 ft-lb |
| 2 3/4 inch, 1 oz | 1,445 fps / 2,028 ft-lb | 1,420 fps / 1,958 ft-lb |
| 3 inch, 260 gr | 1,845 fps / 1,965 ft-lb | 1,830 fps / 1,933 ft-lb |
| 3 inch, 260 gr | 1,915 fps / 2,117 ft-lb | 1,900 fps / 2,084 ft-lb |
| 3 inch, 1 oz | 1,495 fps / 2,171 ft-lb | 1,465 fps / 2,085 ft-lb |
| 3 inch, 1 oz | 1,550 fps / 2,333 ft-lb | 1,540 fps / 2,303 ft-lb |
20 Gauge buckshot: SAAMI reference data
SAAMI lists buckshot by buck size and number of pellets, with one velocity measured at 3 feet from the standard test barrel. It publishes no pellet weight, so no energy is computed for buckshot.
Scroll the table sideways for the remaining columns.
| Shell length, buck size | Number of pellets | Lead buckshot: velocity at 3 ft |
|---|---|---|
| 2 3/4 inch, 3 buck | 20 | 1,200 fps |
| 3 inch, 2 buck | 18 | 1,200 fps |
What the numbers mean for a shot
SAAMI lists 2 shell lengths for the 20 Gauge: 2 3/4 and 3 inch. Its lead shot loads carry from 3/4 oz to 1 7/16 oz of shot and its non-lead shot loads carry from 3/4 oz to 1 1/4 oz. At 3 feet, SAAMI’s lead shot reference velocities are from 980 to 1,390 fps, and its non-lead shot reference velocities are from 1,100 to 1,600 fps.
SAAMI’s rifled slug reference velocities run from 1,540 to 1,810 fps at 3 feet, and its saboted slug reference velocities run from 1,270 to 1,915 fps at 3 feet. Computed from the nominal slug weight, the most energetic slug reference load is the 3/4 oz rifled slug in the 3 inch shell, at 1,800 fps at 3 feet: 2,360 ft-lb. Its buckshot reference loads are all listed at 1,200 fps at 3 feet, with 18 to 20 pellets.
None of the shot or buckshot figures is a pattern, range or energy figure. SAAMI’s tables give shot weight rather than shot size, measure shot and buckshot velocity at 3 feet, and publish no pattern or energy data, so they cannot say how far a load is effective or how hard it hits. The slug energy figures are computed at the test barrel only: SAAMI measures no further than 15 feet, so they say nothing about energy or drop at hunting distances. Each product in our 20 Gauge ammo range lists whatever its maker publishes for that item.
Shell length, chamber and pressure
The maximum average pressure for the 20 Gauge is 12,000 psi in every shell length SAAMI lists. Never fire a shell longer than the chamber of your shotgun. Check the chamber length marked on the barrel or given in the owner’s manual, and match the gauge and shell length printed on the box to it.
SAAMI’s lead shot reference velocities were measured in test barrels with a choke constriction of .031 ± .005 in (0.79 mm ± 0.13 mm), and its non-lead shot velocities in test barrels with .005 ± .005 in (0.13 mm ± 0.13 mm). Those are the barrels every velocity above was measured in, not a statement about your shotgun: your own barrel and choke can give different figures. Check the barrel and choke maker’s instructions before firing non-lead shot, and check the current regulations where you hunt, because rules on which shot may be used, for waterfowl in particular, vary by location.
SAAMI’s rifled slug data is for loads intended to be fired from smooth-bore firearms, and its saboted slug data is for loads intended for use in rifled-barrel shotguns and rifled choke tubes. Match the slug type to your barrel, and check the choke maker’s instructions before firing any slug through a choke tube.
20 Gauge vs 410 Bore: the SAAMI comparison
A figure from one maker’s catalogue cannot be laid beside a figure from another’s: each picks its own test barrel, choke and payload. SAAMI is the shared basis, because it fixes one standard test barrel and one way of measuring velocity for every shotshell it lists.
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| SAAMI specification | 20 Gauge | 410 Bore |
|---|---|---|
| Shell lengths SAAMI lists | 2 3/4 and 3 inch | 2 1/2 and 3 inch |
| Maximum average pressure, 2 1/2 inch shell | Not listed | 12,500 psi |
| Maximum average pressure, 2 3/4 inch shell | 12,000 psi | Not listed |
| Maximum average pressure, 3 inch shell | 12,000 psi | 13,500 psi |
| Lead shot, 3 inch shell | 1 1/8 oz to 1 7/16 oz; 1,100–1,300 fps | 11/16 oz to 15/16 oz; 975–1,135 fps |
| Non-lead shot, 3 inch shell | 7/8 oz to 1 1/4 oz; 1,175–1,600 fps | 3/8 oz; 1,400 fps |
| Rifled slug, 3 inch shell | 3/4 oz; 1,800 fps | Not listed |
| Saboted slug, 3 inch shell | 260 gr to 1 oz; 1,495–1,915 fps | Not listed |
| Lead buckshot, 3 inch shell | 2 buck; 1,200 fps | 000 buck; 1,080 fps |
In the 3 inch shell, SAAMI standardises the 20 Gauge at 12,000 psi and the 410 Bore at 13,500 psi, so the 20 Gauge runs 1,500 psi lower. The heaviest lead shot load SAAMI lists in that shell is 1 7/16 oz for the 20 Gauge and 15/16 oz for the 410 Bore. A higher pressure limit is a ceiling on the load, not a measure of its power.
What SAAMI cannot settle is anything past the muzzle. It publishes no pattern, shot size or downrange data, so it cannot say which gauge is more effective at a given distance; that depends on the load and the choke. We stock the other side of this comparison too: 410 Bore ammo.
20 Gauge ballistics questions
What is the maximum pressure of the 20 Gauge?
ANSI/SAAMI Z299.2 sets the maximum average pressure for the 20 Gauge at 12,000 psi in every shell length it lists.
How fast is a 20 Gauge shotshell?
SAAMI’s reference velocities for the 20 Gauge, measured at 3 feet from the standard test barrel, are from 980 to 1,390 fps for lead shot and from 1,100 to 1,600 fps for non-lead shot.
How fast is a 20 Gauge slug, and how much energy does it carry?
SAAMI’s rifled slug reference velocities run from 1,540 to 1,810 fps at 3 feet, and its saboted slug reference velocities run from 1,270 to 1,915 fps at 3 feet. Computed from the nominal slug weight, the most energetic slug reference load is the 3/4 oz rifled slug in the 3 inch shell, at 1,800 fps at 3 feet: 2,360 ft-lb. SAAMI publishes velocity only, so the energy figure is computed, not published.
What buckshot loads does SAAMI list for the 20 Gauge?
SAAMI lists 2 buckshot reference loads for the 20 Gauge, in buck sizes 2 and 3, carrying 18 to 20 pellets, with a reference velocity of 1,200 fps measured at 3 feet. It publishes no pellet weight, so no buckshot energy can be computed from it.
What is the difference between 2 3/4 and 3 inch 20 Gauge shells?
SAAMI standardises both at 12,000 psi. SAAMI lists lead shot loads carrying from 3/4 oz to 1 1/8 oz in the 2 3/4 inch shell and from 1 1/8 oz to 1 7/16 oz in the 3 inch shell. A shell must never be longer than the chamber of the shotgun it is fired in.
Is the 20 Gauge more powerful than the 410 Bore?
Power is not a SAAMI measure. What SAAMI publishes is a maximum average pressure and the shot weights and velocities of its reference loads. In the 3 inch shell, which both list, the heaviest lead shot load SAAMI lists is 1 7/16 oz for the 20 Gauge and 15/16 oz for the 410 Bore, at maximum average pressures of 12,000 psi and 13,500 psi.
What shot weights does SAAMI list for the 20 Gauge?
SAAMI lists lead shot loads carrying from 3/4 oz to 1 7/16 oz and non-lead shot loads carrying from 3/4 oz to 1 1/4 oz.
What is the effective range of a 20 Gauge?
Effective range is not a SAAMI specification. SAAMI measures velocity at 3 feet and publishes no pattern or energy data, so it says nothing about performance at distance; that depends on the load, the shot size and the choke.
Where to buy these loads
Hilltop Armory carries 20 Gauge ammunition from Winchester, Federal, HEVI-Shot, Remington, Apex Ammunition and Fiocchi. Browse the full 20 Gauge ammo range.
