How Much Does Rain Affect Trajectory?

Discussion in 'Competition Forum (All Calibers)' started by clunker, Jan 17, 2019.

  1. Turbulent Turtle

    Turbulent Turtle F-TR competitor

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    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.
     
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  2. Papa Charlie

    Papa Charlie Gold $$ Contributor

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    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.

    [​IMG]
     
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  3. jr600yd

    jr600yd Gold $$ Contributor

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    Hehehe..... Rain-X.......good one hehehe....
     
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  4. 243BR

    243BR

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    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.
     
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  5. Milo 2.0

    Milo 2.0

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    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.
     
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  6. Bart B.

    Bart B.

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    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.
     
  7. Milo 2.0

    Milo 2.0

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

    Papa Charlie Gold $$ Contributor

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    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.
     
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  9. Bart B.

    Bart B.

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    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.
     
    Last edited: Jan 18, 2019
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  10. skibar_tx

    skibar_tx

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    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.
     
  11. rardoin

    rardoin Silver $$ Contributor

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    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.
     
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  12. Bart B.

    Bart B.

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    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
     
    Last edited: Jan 18, 2019
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  13. dougridgeore

    dougridgeore

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    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.
     
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  14. ED3

    ED3 Gold $$ Contributor

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    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?
     
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  15. Turbulent Turtle

    Turbulent Turtle F-TR competitor

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    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.
     
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  16. VaRandy

    VaRandy

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    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.
     
  17. savagedasher

    savagedasher

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

    VaRandy

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

    Snuggie F/TR-F/Open Gold $$ Contributor

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    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!
     
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  20. skibar_tx

    skibar_tx

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    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.
     

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