How Much Does Rain Affect Trajectory?

[Turbulent Turtle]

Rain equals 100 % humidity.... So you can run the numbers..

Er, no. It is 100% humidity in the clouds where the rain started. It can be any level where you are rained on.

On the plus side, the bullets will be clean when they get to the target.

 

[Papa Charlie]

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.

 

[jr600yd]

Hehehe..... Rain-X.......good one hehehe....

 

[243BR]

Rain equals 100 % humidity.... So you can run the numbers..

I'm not a weather expert (or an expert in anything), but I don't think this is correct. The way it was explained to me is that rain is falling through the air, not becoming part of it. A dense fog is 100% humidity.
I've also heard the shock wave theory.
From my experience, rain does not effect trajectory to any measurable degree.

 

[Milo 2.0]

I'm not a weather expert (or an expert in anything), but I don't think this is correct. The way it was explained to me is that rain is falling through the air, not becoming part of it. A dense fog is 100% humidity.

You may be right, but for all practical purposes, you're about to complicate this. We've all been rained or hailed on while the sun is shining. If skies are grey, no rays of sunshine in sight, and it's drizzling or raining, chances are great that it is 100% humidity in your immediate area.

 

[Bart B.]

Rain equals 100 % humidity.... So you can run the numbers..

Would the amount of rain have any impact? 2 drops per yard of the trajectory versus 10, for example. Rain drops sizes equal for both.

 

[Milo 2.0]

It's a general consensus that rain drops cannot get to the bullet, how about hail?

 

[Papa Charlie]

A relative humidity measurement of 100% does not necessarily mean that rain is falling. It just means that the air is holding as much moisture as it can at a given temperature, in the form of water vapor, which is an invisible gas.

 

[Bart B.]

It's a general consensus that rain drops cannot get to the bullet, how about hail?

Hail will deflect bullets especially when it's bouncing off your barrel as it did some years ago at the Whittington Center range. Some shots didn't go to call. 4 inches of hail in 15 minutes up to near 3/4" diameter that caused accidents on local highways.

I've seen big flocks of birds on the 200 yard line take flight at Camp Perry as the 600 yard stage of a rapid fire match begins. With each of several 6 man teams' members shooting 24 or more rounds in 50 seconds, several birds did fall. Bullets deflected.

 

[skibar_tx]

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.

 

[rardoin]

Rain is a lubricant, i was told this by a very experienced record holder. This is why when a rain starts ur group is higher in elevation, speed is increased,

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.

 

[Bart B.]

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.

I see shock waves only behind the bullet tip. How close to its tip are they?

Really pointed bullet's shock waves start at their tip. Those with round noses have a curved pressure wave in front where the shock wave starts.

https://www.google.com/search?q=bul...KHRWGA7AQ7Al6BAgIEBw&biw=911&bih=683&dpr=2.25

 

[dougridgeore]

In a rain storm...Make sure you have some sort of cover over your ammo and loading port...remember: if it is attached to your rifle it counts as part of the weight.
This cover should be part of your gear before you look up and see the rain coming.
If it is raining real hard wait for at least the half way point to start your string it can only get better. Often you get lucky and it stops...seen it happen...You will still finish in time.
Make sure the hand that grabs your dry ammo stays dry as well and have a dry towel just in case your hand gets wet.

In my observations? it seems everybody with dry cases....generally shoots better in the rain and everybody with wet cases can’t figure out that one weird elevation flyer, that went into the 8 ring.

 

[ED3]

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.

Any thoughts as to why that was? I can understand cold air, being more dense than warm air having some effect on trajectory, as well as powder burn variations...but the presence of snow itself? I can't believe those factors would attribute to 5moa. Don't shoot irons myself, so is there some possibility of an optical illusion occurring?

 

[Turbulent Turtle]

Any thoughts as to why that was? I can understand cold air, being more dense than warm air having some effect on trajectory, as well as powder burn variations...but the presence of snow itself? I can't believe those factors would attribute to 5moa. Don't shoot irons myself, so is there some possibility of an optical illusion occurring?

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.

 

[VaRandy]

Don't know about smaller bullets but I saw a less than 2 inch group shot in an absolute washout . Bullet was .30 215 Berger. I still have trouble believing it but saw it first hand.

 

[savagedasher]

I assume air. Density would change
The rate of The deceleration

 

[VaRandy]

Don't know about smaller bullets but I saw a less than 2 inch group shot in an absolute washout . Bullet was .30 215 Berger. I still have trouble believing it but saw it first hand.

Forgot to Say. This was 1000 yards in IBS warmup session.

 

[Snuggie]

I’ve not had any issues at all shooting in the rain. And I’m shooting a .223 with 90VLD’s. No mirage to deal with until the sun comes up and it gets real hot. Then mirage goes crazy!

 

[skibar_tx]

Any thoughts as to why that was? I can understand cold air, being more dense than warm air having some effect on trajectory, as well as powder burn variations...but the presence of snow itself? I can't believe those factors would attribute to 5moa. Don't shoot irons myself, so is there some possibility of an optical illusion occurring?

I was shooting FTR in a Palma match, I had no optical illusion with a 12-42 power scope. I assumed that the bullet had more resistance going through a solid material. It was real though, everyone all the way down the line was hitting the dirt in front of the target. Everyone shot monthly matches there, they all knew within a moa or so of what their normal elevation would be.