Subsonic ammunition

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Subsonic ammunition is ammunition designed to operate at speeds below the speed of sound, which at standard conditions is 343.2 m/s (1,126 ft/s). This avoids the supersonic shockwave or "crack" of a supersonic bullet, which, particularly for suppressed firearms, influences the loudness of the shot.[1][2]

Subsonic ammunition usually uses heavier bullets to retain as much 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[edit]

Subsonic versions of standard rounds[edit]

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 7.5 grams (116 gr) bullet at velocities typically around 400 metres per second (1,300 ft/s). Subsonic loads for 9mm commonly use 9.5 grams (147 gr) bullets at velocities of 300 metres per second (980 ft/s)*.

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 properly function in such firearms.

Inherently subsonic calibers[edit]

Some ammunition types were inherently designed with heavier, slower standard bullet weights and velocities. For example, the traditional military standard .45 ACP ammunition load, of a 230 grain bullet, was subsonic.

Specialized subsonic calibers[edit]

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 (7.62×35mm), .338 Whisper, 9×39mm, 12.7×55mm STs-130, .510 Whisper.

Use with suppressors[edit]

Combined with firearm sound suppressors, subsonic ammunition may significantly reduce sound levels compared to normal ammunition. Specific reductions depend on the ammunition and suppressor.

References[edit]

  1. ^ Paulson, Alan C (1996). Silencer History and Performance, Vol 1: Sporting And Tactical Silencers. Paladin Press. ISBN 0-87364-909-5. 
  2. ^ Paulson, Alan C; Kokalis, Peter G.; Parker, N.R. (2002). Silencer History and Performance, Vol 2: CQB, Assault Rifle, and Sniper Technology. Paladin Press. ISBN 1-58160-323-1.