When the bullet approaches the transonic range, that is it is moving through the speed of sound the center of pressure starts to move backwards as it slows, and moves towards the center of gravity which remains static. What a lot of people don’t know is that the bullet also has a center of pressure, which is in front of the center of gravity when the bullet is flying at supersonic speeds. The bullet also has a center of gravity, which is in roughly in the centre of the bullet. If you read my article on the RPM of a bullet, you will see that the bullet is spinning on a axis, which runs through the centerline of the bullet. At that speed the air resistance is equal to hitting a brick wall, and the bullet has to move through this, so a pressure wave is created in front, and on the tip of the bullet. When a high powered rifle bullet is fired it’s initial flight is supersonic, that is it is moving faster than the speed of sound. The speed required to break the sound barrier is known as Mach 1, thus Mach 2 is twice the speed of sound, Mach 0.5 is half the speed of sound.Īn interesting fact, the fastest manned flight was done by NASA’S X-43A aircraft on November 16 2004, the aircraft flew at Mach 9.6, almost 7000 mph, which is 11265 km/h. Thus the speed required to break the sound barrier decreases at higher elevations, where the temperature is colder, and the same applies to dryer air, which is less dense. Note the two variables, dry air and temperature! because gas molecules move more slowly at colder temperatures this slows the speed of sound, sound moves faster through warmer air. This is 1,236 kilometres per hour, or a kilometre in 2.914 seconds, or a mile in 4.689 seconds.Īt sea level a generally accepted value is 340.29 m/s, and this value decreases as the altitude increases. Contrary to what a lot of people believe the speed of sound is not a fixed value, in dry air at 20 ☌, the speed of sound is 343.2 metres per second (1,126 ft/s).
Let me state this up front, I am not a ballistics’ engineer, so this is the very basics of what actually happens, but it gives a very good idea of what actually happens to a bullet, and how much design and engineering work is done to find the optimal bullet shape, weight and profile.įirst of all let’s define what the speed of sound is.
What this basically means is that the bullet will be moving faster than the speed of sound, then move through the sound barrier, and then move slower than the speed of sound until the bullet, in theory, comes to a complete stop. Supersonic, Transonic and Subsonic BallisticsĪny bullet fired from a high powered rifle will go through the Supersonic, Transonic and Subsonic phase when fired over extreme range.
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