How Much Does Rain Affect Trajectory?

[Park ranger]

I set up my sprinkler in my yard and shot through it with a 22 LR. Everything from rain like drops to hose full stream of water. At some point, water pushes the bullets. This wasn’t supersonic

 

[Yes F-TR]

I was there at the match Skip shot in the snow. The elevation struggle was real. It was Easter weekend at Ft. Wolters and it was snowing so hard that when we got back to the 1000 yd line they called the match because we couldn't see our targets anymore. We all shot our first sighters and our targets did not go down. It was a very surreal feeling to say the least.

 

[Immike]

I suspect you guys were experiencing a light condition you normally don’t have. If light can bend up by mirage, then surely it can bend down by a opposing condition ... damn interesting testimony from some experienced shooters. A heavy snowfall during a match is rare territory.

 

[Warren Dean]

I'm thinking that the 5MOA was a typo and it was supposed to be 0.5MOA.

5MOA is huge, it will throw you off paper at 1000 yards if your prior shot was in the black.

I'd have to check the BC of the Sierra Palma bullet.

Ahhh. what do you know, Denys?

 

[Warren Dean]

Pretty simple...old service rifle saying...."Lights up, sights up". It matters.

 

[Bart B.]

Pretty simple...old service rifle saying...."Lights up, sights up". It matters.

What's the saying if the light's right? Sights ______.

That's when the left side of the front sight blade is on the shady side.

 

[Bart B.]

I have never seen much change in vertical when shooting in rain. However, snow does affect elevation. Shooting a Palma match in the snow, I had to add about 5 moa of elevation.

I've shot Palma and magnum any rifle matches in snowfall. Sight elevation was the same as cold weather without snow.

 

[spclark]

Please explain.....I have never heard this theory.

Maybe ‘cause when it’s raining the air ‘twixt muzzle and target, is less dense? Idea being water vapor (humidity) is highest around rain drops, water vapor makes bullet passage easier? I dunno...

What I do know is when it rains and I’m on my mat shooting a string it gets really tough trying to see the darn aiming black in my sights. Then there’s the sliding-around elbow in the puddle under my right arm.

 

[Ned Ludd]

I suspect in most cases the rain affects the shooter more than the bullet:

 

[Bc'z]

I suspect you guys were experiencing a light condition you normally don’t have. If light can bend up by mirage, then surely it can bend down by a opposing condition ... damn interesting testimony from some experienced shooters. A heavy snowfall during a match is rare territory.

Yes there is mirage from heat as well as cold.

 

[Warren Dean]

What's the saying if the light's right? Sights ______.

That's when the left side of the front sight blade is on the shady side.

The light "pushes" the sight picture. Easier way to remember.

 

[Bart B.]

Anyone ever reduce the military NM rear sight aperture down to about .040" from .0520" or .0595"? Shure makes the sight picture sharp and clearer on bright days.

 

[243BR]

Not quite how it works.....

Higher humidity = less air density
Less air density = lower drag
Lower drag = less velocity decay which equals higher velocity at the target relative to a lower humidity assuming all other factors remain the same. The speed of the projectile would not increase...which implies acceleration....it just decelerates at a lesser rate. As far as the lubricant theory I strongly feel your friend is mistaken.

Higher humidity = less air density?
Is that correct?
I'd think it would be the opposite. Just askin'.

 

[Toby Bradshaw]

Higher humidity = less air density?
Is that correct?
I'd think it would be the opposite. Just askin'.

A molecule of water (H2O) weighs 18 daltons, whereas the molecules of nitrogen (N2) and oxygen (O2) that are displaced by H2O vapor weigh 28 and 32 daltons, respectively. Ergo, the higher the water vapor content of the air (humidity) the lower the air density.

 

[Bart B.]

The light "pushes" the sight picture. Easier way to remember.

Which way for my question?

 

[4xforfun]

Living here in the PNW I have shot in some very heavy rains, been so bad could hardly make out the target let alone the X. The winds died to zero and the string was amazing. I can't say the rain helped but if there was any wind you would have been able to see it and identify the angle and strength very easily.
As far as the rain affecting the bullet in flight, a bullet traveling at supersonic speed creates a shock wave in front of it that travels back like a cone. This wave would prevent any rain drop from contacting the round during flight and therefore would have absolutely no affect on the trajectory. Here is an image of this wave.

The problem is.......if you disrupt the sonic cone in front of the bullet, you affect the bullet. Just because the bullet doesn't actually touch the drop it still affects the flight.

 

[rardoin]

Higher humidity = less air density?
Is that correct?
I'd think it would be the opposite. Just askin'.

Yes, correct. Initial instincts would lean opposite but explained eloquently in post #54- thanks T.B.

 

[6MMsteve]

my brother and I always tried to go to PA 1000 yd when A Low Pressure system or rain was in the forecast

 

[riflewoman]

I shot for years it the great Pacific NorthWet.. what I found the biggest issue with rain is visibility. With rain generally comes mist and fog. Zeros remained, but damned difficult to see.

 

[Immike]

Which way for my question?

You will shoot away from the light due to a false image on inside of the metallic site.
Example: if the sun is on your left then you tend to shoot right.