Bullet contrail was unreal today (5.56)

[jbdesigns]

Must take the whole 2 is 1 and 1 is none pretty seriously. Good man.

Ha ha. Their extra girlfriend and the newly graduated doctors boyfriend. My married 51year old ass has zero girlfriends.

[jbdesigns]

I saw something similar to what you're describing in one of tnoutdoors videos (below), and think it would be pretty awesome to see in real life. The "trails" can be seen at about the 3:00 mark. I don't think he realized it until after viewing the footage, so that's pretty cool that you were able to catch this in real time. How would you say this compares to what you experienced today?

https://m.youtube.com/watch?v=ZxpnWftvCTo

Not like tnoutdoors. Ours was smokey like, not like his video. The girls were taking videos, I'll get their footage and see if anyone captured it.

[cutter_spc]

I saw this happen once while a friend was shooting (16" carbine), looked as if the bullet was trailing smoke, not unlike the early aircraft tracers in the black an white films. If I remember right he was using Federal 223 ammo, had a black polymer tip, always meant to pick some of that ammo up as I thought it was the ammo.

[Straight Shooter]

Ive seen this a few times. One time stands out, it was a hot, terribly humid, muggy day at the range. Friend of mine shooting a bolt 22-250.
Every shot was a solid line of blue smoke out to 100 yards, with the accomplying mirage type effect. Was awesome.

[Kdubya]

Not like tnoutdoors. Ours was smokey like, not like his video. The girls were taking videos, I'll get their footage and see if anyone captured it.

That'd be awesome if you guys managed to catch it on film. Yours definitely sounds more pronounced. Looking forward to the potential footage!

[lysander]

It happens when the relative humidity is very high. You see it more commonly with aircraft propellers, as someone else here mentioned.

At any given time, the air can only hold some much humidity before the humidity condenses out as visible water droplets. How much water is in the air is measured as relative humidity. Once relative humidity hits 100%, the air cannot hold any more water and any additional water in the air over the amount that the air can contain condenses out as water droplets. These water droplets are very, very small, and can still stay suspended in the air; however, they become visible as trails, clouds, etc.

Enter aerodynamics.

When a bullet is travelling through the air, it is aerodynamically generating a very, very slight amount of lift (or an area of low pressure, technically). The lift itself is mostly cancelled out by other forces, but the low pressure remains. When the pressure of the surrounding air is lowered, the temperature drops; when the air temperature drops, the air can hold less water due to the lessened energy state of the air, but the amount of absolute water vapor in the air remains the same. This has the effect of raising the relative humidity.

On days when the relative humidity is very, very close to 100%, quickly dropping the air pressure will cause the water vapor to condense out. As mentioned earlier, this is commonly seen with aircraft, but can also happen with bullets, arrows, and anything else that has or creates a lifting surface or area of low pressure as it travels through the air.

On a day like this, the bullet will create a contrail of sorts that will spin with the bullet due to the wake turbulence the bullet is leaving behind. Depending on the atmospheric conditions, the amount of time it's visible is usually very brief, but can vary. Once the bullet has left the immediate area (which is measured in milliseconds given the speed of the projectile), the air pressure will return to normal and the water vapor will evaporate back into the air as the temperature rises back to the ambient temperature.

Given that you were in a marshy area (inherently high relative humidity) on a cool, stable day, this is likely what you saw.

Too bad you didn't get film of it - would've made for some good YouTube.

There is also the pressure drop across the shock wave in front of the bullet....

[HeruMew]

Sounds like an awesome environmental phenomenon to have occur.

Would love to see it if you caught it on film.

[JoshNC]

Skyyr that was the best explanation of bullet contrail/trace I've ever read....thank you!

[jbdesigns]

Apparently no one captured this on video. They would video the shooter,not down range ��

I also think this was my Mexican match. I pulled m855 bullets and seated a 69 grain hornady match bullet instead. I also re dropped the powder about .5 grains less. To account for slightly heavier bullet and to be more consistent. I weighed a dozen charges and there was too much variation for my tastes.

[FromMyColdDeadHand]

I wonder if the speed the the flatness of the bullet base makes any difference. More severe wake cavitation behind the bullet? That might help explain the 53s.

I've also noticed in humid conditions that after a string of fire in a High-Power match, it is easier to see your breath if the temp is low and humidity high. I always thought it was due to particulates in the air from all the firings giving the breath something to condense on. Maybe since it is spring time, general pollen in the air helped to trip the condensation.

I can't believe that in this day and age no one took a video...