Subsonic ammunition
Subsonic ammunition is ammunition designed to operate at velocities below the speed of sound (Mach 1), which at standard conditions is Script error: No such module "convert".. This avoids the supersonic shockwave or "crack" of a supersonic bullet, which, particularly for suppressed firearms, influences the loudness of the shot.[1][2][3]
Subsonic ammunition usually uses heavier bullets to retain as much kinetic energy as possible at the lower velocities. Some subsonic ammunition is used in non-suppressed firearms to gain the advantages of heavier bullet weights.
Standard calibers
Subsonic versions of standard rounds
In this instance, heavier bullets are loaded in standard ammunition, which reduces muzzle velocity below the speed of sound.
As an example, the very common 9×19mm Parabellum standard military round is a Script error: No such module "convert". bullet at velocities typically around Script error: No such module "convert".. Subsonic loads for 9×19mm Parabellum commonly use Script error: No such module "convert". bullets at velocities of Script error: No such module "convert"..
For these ammunition loads, balancing bullet weight and velocity are required to ensure that the ammunition will still reliably cycle semi-automatic firearms. Subsonic ammunition with normal bullet weights often fails to function properly in such firearms.
Inherently subsonic calibers
Some ammunition types were inherently designed with heavier, slower standard bullet weights and velocities. For example, the traditional American military standard .45 ACP ammunition load of a Script error: No such module "convert". bullet at Script error: No such module "convert"., is naturally subsonic.
Specialized subsonic calibers
Alternatively, specialized firearms and ammunition may be used to optimize total subsonic ammunition effectiveness. These are designed from the start as dedicated subsonic projectile systems. Some examples include .300 Whisper, 300 AAC Blackout, .338 Whisper, 8.6mm Blackout, 9×39mm, 12.7×55mm STs-130, .500 Whisper, and .510 Whisper.
Use with suppressors
Script error: No such module "Labelled list hatnote". Combined with firearm sound suppressors, subsonic ammunition may significantly reduce sound levels compared to normal ammunition.[4] Specific reductions depend on the ammunition and suppressor.
The peak sound pressure levels of a Remington 700 .223 caliber bolt-action rifle firing high-velocity (supersonic) ammunition using a GEMTECH G5-5.56 suppressor.
| Suppressor Condition | Muzzle (dB SPL) | Left Ear (dB SPL) | Right Ear (dB SPL) | Behind Shooter (dB SPL) |
|---|---|---|---|---|
| Unsuppressed | 176 | 160 | 160 | 148 |
| Suppressed | 148 | 134 | 136 | 120 |
| Reduction | 28 | 26 | 24 | 28 |
The peak sound pressure levels of a Remington 700 .223 caliber bolt-action rifle firing low-velocity (subsonic) ammunition using a GEMTECH G5-5.56 suppressor.
| Suppressor Condition | Muzzle (dB SPL) | Left Ear (dB SPL) | Right Ear (dB SPL) | Behind Shooter (dB SPL) |
|---|---|---|---|---|
| Unsuppressed | 157 | 140 | 140 | 127 |
| Suppressed | 131 | 122 | 120 | 100 |
| Reduction | 26 | 18 | 20 | 27 |
Compared to the high-velocity (supersonic) unsuppressed condition, the combination of subsonic low-velocity ammunition and a firearm suppressor provided reductions of 45, 38, 40, and 48 dB, peak sound pressure level at the muzzle, left, right ears and behind the shooter, respectively.[4]
References
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- ↑ Shooting Range Industries. Shooting Terms; What Is Bullet Drag, Bow Shockwave, Mach Speed Number, Boat Tail & More - Shooting Range Industries. [online] Available at: <http://www.shootingrangeindustries.com/shooting-terms-what-is-bullet-drag-bow-shockwave-mach-speed-number-boat-tail-more/>
- ↑ a b Script error: No such module "Citation/CS1".
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