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Posted: 9/12/2009 5:35:36 PM EDT
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Oddly, a google search turned up few results on this. Went shooting today and the rain varied from a light sprinkle to a pretty steady downpour. I was shooting .223 55gr bullets and it SEEMED like my POI was off. On a dry day with this same rifle and the same ammo, I am zeroed at dead center at 100 yards. With the rain, I was anywhere from 2-3" low to 4-6" low on POI using the same sight picture. The ammo was the Centurion 55gr bulk stuff, so I think it rates around 2700FPS according to the review thread in the ammo forum. So there's my question. Can rain have an effect on bullet flight? To widen the scope, let's look at this from "a little rain" to "complete downpour" or even "what if you were to shoot through a waterfall?". Any thoughts? |
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well just think about it a minute.
the gun is zeroed shooting through a medium(air) of a certian density. now you add a heavy rain at 100yards. how much extra mass(water) does that projectile now come in contact with? with those lite projectiles, i could see a heavy rain effecting poi. or you could have just had an off day. i'll shoot in the rain, but never looking for super groups. just can't get as comfortable, or relax as much. |
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Quoted: well just think about it a minute. the gun is zeroed shooting through a medium(air) of a certian density. now you add a heavy rain at 100yards. how much extra mass(water) does that projectile now come in contact with? with those lite projectiles, i could see a heavy rain effecting poi. This was my initial guess, but this same discussion from other forums that I read first came to the conclusion that a few things may be happening: 1. The bullet is simply flying too fast to be influenced by rain drops. (Somewhat plausible?) 2. The bullet never comes in contact with rain drops because of the space between rain drops. (This is ridiculous, imo. AFAIK rain is random so there is always a possibility that the two come into contact at some point) [They noted that during WWI some planes had MGs mounted behind the props and would shoot through the prop without damaging it, so it is a similar situation.] (I have no idea on this) 3. The bullet forms a "shield" of air around it that deflects rain drops as it flies through the air. (Not sure) |
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Quoted:
Quoted:
well just think about it a minute. the gun is zeroed shooting through a medium(air) of a certian density. now you add a heavy rain at 100yards. how much extra mass(water) does that projectile now come in contact with? with those lite projectiles, i could see a heavy rain effecting poi. This was my initial guess, but this same discussion from other forums that I read first came to the conclusion that a few things may be happening: 1. The bullet is simply flying too fast to be influenced by rain drops. (Somewhat plausible?) 2. The bullet never comes in contact with rain drops because of the space between rain drops. (This is ridiculous, imo. AFAIK rain is random so there is always a possibility that the two come into contact at some point) [They noted that during WWI some planes had MGs mounted behind the props and would shoot through the prop without damaging it, so it is a similar situation.] (I have no idea on this) 3. The bullet forms a "shield" of air around it that deflects rain drops as it flies through the air. (Not sure) the machine guns had a mechanical interupter so they could not fire when the prop was in the way |
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Bullets will hit rain drops. I remember shooting pistols in a downpour and watching the tracer-like effect of the bullet's flight though the rain.
It makes sense that you will get some deflection when the bullet hits a raindrop. Not sure a light rain would account for a 3-6" POI shift at 100 yards though. |
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Quoted:
The Germans had the interupters first. The rest armored their props to begin with. Guess which plane went faster? I believe the Brits added the interupters after knocking down a few German planes and finding out the secret. Correct. It's called the Fokker interrupter gear. The Brits captured a Fokker triplane more or less intact, which let them figure it out. |
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Humidity also has a small effect on a bullet’s trajectory, and at all altitudes. Humidity affects the air density, tending to decrease the air density a small amount, depending on the relative humidity in the atmosphere and the vapor pressure of water at the temperature of the atmosphere. The effect of humidity is generally worst at locations near sea level on very hot days, but even under these conditions, the effect is small.
From here. It's pretty humid when it's raining. GL |
| I think the bow shock would break up the rain drops before the bullet actually hit them. Kind of like trying to shoot a blade of grass with a 22, the blade always moves out of the way. It would look the same as hitting the raindrops, but wouldn't actually touch them. At 100 yds I think the effect of humidity would be negligible, or at least not 2-4 MOA. My guess is it's a visibility issue. |
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It does, but it is so minor and random you cannot adjust for it.
The M739A1 quick fuze used on artillery rounds actually had to be redesigned to add foil that ruptured and a defuser at the tip because hitting water drops in flight was enough to set the round off after it had armed. |
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Quoted:
In before someone says "the rain will hit the top of the bullet and knock it farther down". In advance, it won't happen because the bullet is falling down just as fast as the rain drops are. Thats not true. a) The bullet is fired at an angle and will travel above your line of sight(depending on the range of the target and zero on the rifle). b) You may be confused with some basic physics. Objects have the same acceleration due to gravity(before reaching terminal velocity), but not the same velocity. A raindrop has likely reached its terminal velocity long before coming anywhere near your projectile. |
we all do that
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I shoot in a summer long every tuesday league that is 100 yards rimfire . we have a covered shooting position and several times have hung the targets and got set up just as the rain was hitting . We have shot in pretty hard rain and it doesn't seem to make a difference (except when the wind is blowing) Now we are shooting 40 shot matches with a 1" 10 ring so we would notice if it had any effect.
It kind of goes against logic, I can't explain why but 8 or ten folks all shooting 40 shots plus sighters without any shots going astray shows me that there is somehow little to no effect And before someone asks, there was no treadmill involved |
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Quoted:
I shoot in a summer long every tuesday league that is 100 yards rimfire . we have a covered shooting position and several times have hung the targets and got set up just as the rain was hitting . We have shot in pretty hard rain and it doesn't seem to make a difference (except when the wind is blowing) Now we are shooting 40 shot matches with a 1" 10 ring so we would notice if it had any effect. It kind of goes against logic, I can't explain why but 8 or ten folks all shooting 40 shots plus sighters without any shots going astray shows me that there is somehow little to no effect And before someone asks, there was no treadmill involved It does but it is so small that is barely perceivable and it create a angular shift. Angular errors manifest themselves as range increases, so you will see less of it as range diminishes. |
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