Effects of rain on light projectiles

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by skip300, Feb 5, 2011.

  1. skip300

    skip300 Member

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    Im sure this has been covered not only here but in many forums over the years but I thought I would report my findings.

    Today I was firing 32gn .204 projectiles at roughly 3900fps during light rain. First shot hit the target like a shot gun. Bullet exploded.
    After that bullets consistently hit lower and to the direction of the wind which was clearly visible by the rain, although the wind was not bad, maybe the rain exagerated the effects onto the projectile?
    I adjusted for this factor and I was back on target. Then when the rain had stopped the bullet shot the opposite to the adjustments I had made and shot high and in the opposite direction of the wind. The adjustments were reversed.
    Re-adjusted and back on target.
    Next it began to rain really heavy with no wind. Bullets impact shifted spot on vertically but two inchs low.

    Target distance, 150yrds

    Me scratches me head [​IMG] [​IMG]
     
  2. Hntbambi

    Hntbambi Well-Known Member

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    The rain is denser than air and has a similar effect as wind. While you are not shooting through water the entire distance you are hitting some drops. Did you ever see the Mythbuster episode where they shoot guns into the pool? If I remember correctly, all of the bullets fragged. So a thin jacketed varmint bullet that is supposed to frag did so when it impacted enough water drops. Other shots did not impact as many or drops as big and did not break up. Ballistic crap shoot. I would think it would take a very heavy rain to frag bullets though.

    The lower impact from rain with no wind makes sense, as does the rain with wind deflection. The rain is slowing the bullets down and giving then an external down force along it's path.
     

  3. Mikecr

    Mikecr Well-Known Member

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    I can't think of anything ballistically that would cause your POI to shift like that.
    Especially at only 150yds.

    I shoot in the rain as I shoot any other time, no problems.
    Wet air is actually lower in density overall.
     
  4. dwm

    dwm Well-Known Member

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    Pretty sure I saw pictures in one of the ballistic books that showed the pressure wave in front of the bullet moving the water droplets out of the way.

    Bullet never gets wet. :rolleyes:
     
  5. threejones

    threejones Well-Known Member

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    + I saw the same thing, but can't remember where.
     
  6. zkodiak

    zkodiak Well-Known Member

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    would love to see pics of the rain and it's effect on the bullet. if you find them
     
  7. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Skip,

    One thing that's already been lightly touched on here, but bears repeating; moist air is less dense than dry air. We're not talking about actual water in the air, but water vapor. In the case of rain, you also need to factor in why it's raining. It rains because there's moisture in the air, and the barometric pressure drops. Changes in barometric pressure can cause some radical shifts in impact, though I'd be surprised to see it this pronounced at only 150 meters. If there's a noticable shift in impact, that's the first factor that I'd be looking at, not the raindrops themselves.
     
  8. justgoto

    justgoto Well-Known Member

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    I have a picture and video.

    Here is the picture of me hitting a raindrop.
    [​IMG]

    That little cloud is the hit on a raindrop.

    Here is a video I took today shooting in the rain;
    [ame="http://www.youtube.com/watch?v=dFyQLS2KXBc"]Rain Can Make a POI Difference - YouTube[/ame]

    I made the video as a response to a post on another firearms forum and remembered this thread.
    If the rain is heavy enough and dependent on how many raindrop strikes made, and where along the bullet path the drops are stricken, a great POI shift can be noticed.

    The video shows my 2 shots this morning with the Winchester 94 30-30, at a 7 inch target, 350 yards downrange, in the freezing rain; I missed the first shot, but tagged it on the second.

    The first shot hit a raindrop within 100 yards of the muzzle so it had a big difference on the POI downrange. I aimed exactly as I would have if I was shooting in clear weather and hit about 12 inches low.

    The second shot I aimed higher by about 12 inches expecting to hit raindrops, and expecting a drop in velocity and in turn POI.
    On the second shot I hit 2 raindrops, one looked to be about at the midway point, the other very close to the target, (hard to see in the video,) so they did have an effect, but probably not as much as the first shot.

    I have shot in the rain a lot, when it is light rain the odds of hitting raindrops aren't too great, so you may not see a POI shift. In a heavy rain you are going to hit at least one drop, dependent on how close to the target it is will dictate how much of a POI shift there may be.

    I never would have known how little of a chance there was in hitting a raindrop, if I didn't record my shots.
     
  9. MontanaRifleman

    MontanaRifleman Well-Known Member

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    The mathematical odds of hitting a rain drop, in even in a heavy rain to 100 yds are extremely small. Not impossible but extremely small.

    Cool video Justgoto
     
  10. justgoto

    justgoto Well-Known Member

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    Thank you!

    I made another after the rain subsided as to rule out other conditions.

    [ame=http://www.youtube.com/watch?v=Up-Mq4tbpnM]Rain Can Make a POI Difference 2 - YouTube[/ame]

    I used the same POA as the first shot in the first video, and hit about 2 inches from the second shot's POI. I'm convinced the raindrops made for a profound POI deviation.
     
  11. MontanaRifleman

    MontanaRifleman Well-Known Member

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    That change in POI is quite interesting for sure. I'll have to do some rain testing myself someday. Good thing we don't get much rain here Montana :)
     
  12. Canadian Bushman

    Canadian Bushman Well-Known Member

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    Thats amazing.
     
  13. justgoto

    justgoto Well-Known Member

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    I've made a video testing the POI of bullets hitting drops of water as opposed to those not hitting water... I thought it might be of interest.

    [ame="http://www.youtube.com/watch?v=UusiTSu1tSU"]Does Rain Affect POI? - YouTube[/ame]

    Specifics:
    Howa 1500 30-06
    Hornady 150gr FMJ, 2600fps
    Varget 46.6gr
    CCI 200
    Winchester case
    300 yards
    Dropper devise 260 yards from target

    Shots 3, 4, 5, 6, 8, and 9; hit water drops. They make an 8 inch group.
    Shots 1, 2, 7, and 10; did not hit drops. They make a 1.5 inch group.
    The group that hit water drops, is over 5 times the size of the group that didn't.

    Note:
    I thought shot 8 missed a drop, otherwise I would have taken shot 9 without water as I did shot 10. I couldn't see the water hits on the camera so I speculated from the POIs on how many hits on drops I had accomplished.

    I had preformed this test before; but it was very hard to see the hits in the other video, you can see the hits on drops in this video perfectly.
    The other video basically mirrors this test.

    I also wanted to note that a drop of water seems to simply deflect the bullets. I expected the POI height to be lower due to a velocity reduction; I don't think that is the case anymore. The POI shift appears to be random which denotes simple deflection.
     
    Last edited: Mar 28, 2013
  14. RTK

    RTK Well-Known Member

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    Nice video