# Transonic phase?

#### Creedmoor shooter

##### Well-Known Member
I've been trying to dig up some info on the transonic phase of a bullet. I'm can't find a straight answer on what velocity a bullet goes transonic. Ive read anywhere from 1100-1350ish fps. Is there a specific number? Does transonic period change with different elevations? Atmospheric conditions? I'm right around 1000ft. Reason I ask is I want to push my 6.5 to its furthest limits while remaining super sonic.

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#### Canhunter35

##### Well-Known Member
I understand transonic to mean the period when the bullet slows below the speed of sound...around Mach 1, but air temp and humidity affect the speed of sound so as basically air density changes it changes where your bullet goes transonic...that’s how I understand it anyways

##### Well-Known Member
I've been trying to dig up some info on the transonic phase of a bullet. I'm can't find a straight answer on what velocity a bullet goes transonic. Ive read anywhere from 1100-1350ish fps. Is there a specific number? Does transonic period change with different elevations? I'm right around 1000ft. Reason I ask is I want to push my 6.5 to its furthest limits while rema8ning super sonic.

There isn't an exact number because the speed of sound changes as the density of the air changes stay above 1300 and you should be good

#### Schnyd112

##### Well-Known Member
My ballistic calculator give me a mark where the bullet transitions. Today it is between 1275 and 1284 yards.

#### Garycrow

##### Well-Known Member
There isn't an exact number because the speed of sound changes as the density of the air changes stay above 1300 and you should be good

The speed of sound actually changes with temperature, not air density. Generally at higher altitudes it's colder so the speed of sound is less and people assume it's because the air is less dense, but it's really because of the temperature.

Picking nits I know.

The velocity at which a bullet goes transonic is going to vary by bullet since it's dependent upon shape. Some bullets will start to enter the transonic region at higher velocities than others. I don't know where you'd look to find that info though, maybe the bullet manufacturers would have it.

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##### Well-Known Member
The speed of sound actually changes with temperature, not air density. Generally at higher altitudes it's colder so the speed of sound is less and people assume it's because the air is less dense, but it's really because of the temperature.

Picking nits I know.
Thanks for the correction
I was wrong, density in fluids and solids, temperature in an ideal gas. None of its really practical for these purposes beyond knowing that at sea level speed travels at 1120fps and moves slower in most other conditions so if you use that as your worst case scenario you shouldn't run into an issue.

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#### Creedmoor shooter

##### Well-Known Member
Thanks for the info guys, I figured all this played a part into it. What's a safe bet on velocity at 1000ft?