Ammunition designed to travel at speeds below the speed of sound, typically around 1125 feet per second (at sea level), offers a distinct characteristic in firearms applications. Projectiles of this type, when fired, do not break the sound barrier. This absence of a sonic boom is a key defining feature. As an example, a 9mm round traveling at approximately 1050 feet per second would be considered in this category.
The strategic importance of projectiles moving at speeds below the speed of sound stems primarily from the reduced noise signature produced when fired. This attribute makes them valuable in scenarios where minimizing detection is paramount, such as covert operations or hunting applications where preventing disturbance to wildlife is desired. Historically, development of ammunition in this class has been driven by both military and civilian needs for quieter firearms.
