What is subsonic ammo?
Quick answer: subsonic ammo is loaded so the bullet travels slower than the speed of sound, so it does not make the supersonic crack a faster bullet creates. There is no single fps cutoff, because the speed of sound in air depends on temperature: about 1,086 fps in dry air at 0 C (32 F) at sea level, converted from NASA's 331 m/s, and about 1,128 fps at 68 degrees at sea level, per CCI. Subsonic is quieter, not silent, and NIOSH researchers still advise hearing protection.
Makers offer subsonic loads across rimfire, handgun and rifle cartridges. CCI offers several 22 LR loads with muzzle velocities slower than the speed of sound. Hornady's 2019 announcement lists a 9mm Luger 147 gr XTP among its subsonic handgun loads. Savage Arms names 300 Blackout and 9mm as cartridges with several subsonic loadings, and writes that larger hunting cartridges often won't feature them. Federal makes subsonic loads in 308 Win., 30-30 Win. and 45-70 Govt.
What does subsonic mean?
Savage Arms puts it plainly: subsonic ammo is ammunition where the bullet is travelling less than the speed of sound. The supersonic crack you hear when shooting is created when a bullet travels faster than sound. A subsonic load does not carry that signature crack, which makes the shot quieter.
NASA uses the same word for aircraft. Aeronautical engineers call the ratio of an aircraft's speed to the speed of sound the Mach number, and when an aircraft moves much slower than the speed of sound, conditions are said to be subsonic. Near the speed of sound, NASA calls them transonic. Ammunition uses the word more simply: Savage Arms's definition only asks that the bullet travel slower than the speed of sound, a Mach number below 1.
Savage Arms describes two ways makers get there. Subsonic ammo often uses heavier projectiles than standard velocity ammunition, and it may be loaded with less powder. Both techniques can be used, and often are combined.
How many fps is subsonic?
It depends on the air. NASA states that the speed of sound in air depends on the type of gas and the temperature of the gas, and that under normal atmospheric conditions the temperature, and thus the speed of sound, varies with altitude. So the line a bullet has to stay under moves with the weather and the elevation.
- 0 C (32 F), dry air, sea level: NASA gives a theoretical 331 m/s, which is about 1,086 fps (331 x 3.2808).
- A standard day at sea level: NASA gives about 1,100 feet per second.
- 68 degrees at sea level: CCI gives about 1,128 fps.
Makers round the line differently too. Savage Arms says around 1,100 fps, and one CCI article describes subsonic 22 LR velocities as slower than 1,125 fps. A bullet moving at 1,100 fps would be above the 0 C figure and below the 68 degree figure. Savage Arms notes that boxes of subsonic ammo often list velocities around 1,050 fps or lower.
Subsonic vs supersonic at a glance
| Feature | Subsonic | Supersonic |
|---|---|---|
| Bullet speed | Less than the speed of sound (Savage Arms) | Faster than the speed of sound (Savage Arms) |
| The crack | No supersonic crack, so the shot is quieter (Savage Arms) | The crack you hear is created when the bullet travels faster than sound (Savage Arms) |
| Bullet weight, 300 Blackout example | Many loadings in the 200 to 220 grain range (Savage Arms) | 125 to 150 grains for a standard velocity loading (Savage Arms) |
| Muzzle energy | Not the same muzzle energy as conventionally loaded cartridges (Hornady) | The baseline Hornady compares against |
| Longer range | Drops off faster at longer ranges (Savage Arms) | The baseline Savage Arms compares against |
| Recoil | Lower, from a smaller powder charge (Savage Arms); less recoil (CCI) | The baseline both makers compare against |
| Semi-auto cycling | Some semi-autos may have issues cycling it (Savage Arms); Quiet-22 may need manual cycling (CCI) | Not covered by the sources behind this guide |
Why heavier bullets, and what slower costs
Savage Arms uses 300 Blackout as its example: many subsonic 300 Blackout loadings feature bullets in the 200 to 220 grain range, while a standard velocity loading often uses 125 to 150 grains. Federal's own subsonic 300 Blackout listing shows a 190 grain bullet at 1,000 fps.
The cost is energy. NASA gives the formula for kinetic energy as E = 1/2 m v squared. Because speed is squared and
mass is not, the same bullet at half the speed carries one quarter of the energy, while doubling the mass only
doubles it. Hornady says the same thing about its own line in plain words: This is subsonic, i.e., reduced
velocity ammunition and will not produce the same muzzle energy as conventionally loaded cartridges.
Savage Arms lists two more costs. Slower bullets drop off faster at longer ranges, and if you switch between higher velocity ammo and subsonic rounds, you will need to re-zero your rifle for the point of impact shift. On the other side, Savage Arms and CCI both list lower recoil, which Savage attributes to the smaller powder charge.
Common subsonic cartridges
These are maker examples, not a complete list and not recommendations.
- 22 LR: CCI offers several subsonic 22 LR loads. Its Quiet-22 pushes a 40 grain lead round nose bullet at 710 fps, and its Sub-Sonic HP reaches 1,050 fps with a hollow point. See our best 22LR ammo roundup for the velocity classes on the cards there.
- 9mm Luger: Hornady's 2019 announcement of its 2020 products lists a 9mm Luger 147 gr XTP among its subsonic handgun loads. For 9mm practice loads, see best 9mm range ammo.
- 45 Auto: the same Hornady announcement lists a 45 Auto 230 gr XTP as a subsonic handgun load.
- 300 Blackout: SIG SAUER's 2016 announcement mentions both subsonic and supersonic 300BLK rounds, so the cartridge name alone does not tell you the speed class. Read the box.
- Rifle cartridges: Federal makes subsonic loads in 308 Win., 30-30 Win. and 45-70 Govt., and each of those loads shown on its subsonic page lists 1,000 fps.
Will subsonic ammo cycle a semi-automatic?
Not always. Savage Arms explains that some semi-auto firearms may have issues cycling subsonic ammo due to less available gas in the system to cycle the action. CCI's 2021 catalog says its Quiet-22 cartridges may be used in semi-automatic firearms, however manual cycling of the action may be required. CCI makes a separate Quiet-22 Semi-Auto, loaded a little hotter to allow efficient cycling in semi-autos, which leaves the muzzle at 835 fps. CCI's warning is for that product, and Savage says some semi-autos, not all. Savage's advice is to check that the rounds work in your firearm before relying on them.
Hearing safety
A gunshot makes more than one sound. Slowing the bullet removes its crack. NIOSH writes that firearm suppressors reduce the muzzle blast of a gunshot through a series of baffles contained in a canister. That muzzle blast is a separate sound from the crack of the bullet.
Even with that reduction, NIOSH found that firearm suppressors may reduce noise exposure, and the cumulative exposures of suppressed firearms can still present a significant hearing risk. Its conclusion is direct: firearm users should always wear hearing protection whenever target shooting or hunting. NIOSH's advice names no exception for ammunition type.
How we wrote this: every fact on this page comes from NASA education pages, NIOSH research published through the CDC, and maker sources (Savage Arms, CCI, Hornady, Federal and SIG SAUER). Sources are named in the text, not linked. The 1,086 fps figure and the energy examples are our own arithmetic, shown on the page. This guide explains terms only; it is not buying, legal or hunting advice. See our methodology.
FAQ
Is subsonic ammo silent?
No. Savage Arms says subsonic ammo makes the shot quieter because it lacks the crack of a supersonic bullet, and Hornady says it doesn't have the loud report of a supersonic round. Quieter is not silent. A NIOSH study found that the cumulative exposures of suppressed firearms can still present a significant hearing risk, and it says firearm users should always wear hearing protection whenever target shooting or hunting.
What fps is subsonic?
There is no single number, because the speed of sound in air depends on temperature. NASA gives 331 m/s in dry air at 0 C at sea level, about 1,086 fps by our conversion. CCI gives about 1,128 fps at 68 degrees at sea level. Savage Arms rounds it to around 1,100 fps and says subsonic boxes often list velocities around 1,050 fps or lower.
Is 22LR subsonic?
Not all of it. One CCI article describes subsonic 22 LR as slower than 1,125 fps and sets it apart from standard and high velocity loads; another CCI article lists its Standard Velocity load among its subsonic options. Two CCI examples: Quiet-22 at 710 fps and Sub-Sonic HP at 1,050 fps. Read the velocity on the box rather than assuming.
Does subsonic ammo need a suppressor?
Subsonic describes the bullet's speed. Savage Arms writes that subsonic ammo can help cut down on the noise at a crowded public range or near close neighbors. NIOSH writes that firearm suppressors reduce the muzzle blast of a gunshot through a series of baffles contained in a canister, a different sound from the crack of a supersonic bullet. This guide does not cover suppressor rules or selection.
Is subsonic ammo less powerful?
Hornady says so about its own line: its disclaimer says its subsonic ammunition will not produce the same muzzle energy as conventionally loaded cartridges. The physics is the kinetic energy formula NASA teaches, E = 1/2 m v squared: because speed is squared, the same bullet at half the speed carries one quarter of the energy. Heavier bullets offset part of that loss.
Will subsonic ammo cycle my semi-auto?
Not always. Savage Arms says some semi-auto firearms may have issues cycling subsonic ammo because there is less gas to cycle the action. CCI's 2021 catalog notes that manual cycling of the action may be required with its Quiet-22 in semi-automatic firearms, and CCI loads Quiet-22 Semi-Auto a little hotter, at 835 fps, to allow efficient cycling. Savage advises checking the rounds work in your firearm first.
Next: all guides · best 22LR ammo · best 9mm range ammo · best 9mm self defense ammo.