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Old September 18, 2005, 07:33 PM   #1
TysonTB
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How much does rain affect accuracy?

Okay so after discussing with my brother about trying out the outdoor range in our area it got me thinking about shooting in the rain. Im sure that the lowered visibility would affect accuracy to a certain extent, but lets say for example there was nothing to limit visibility. Would the rain change the bullets trajectory after hitting a raindrop or does it just go so fast that it doesnt hit the rain? In the same way that a sniper would have to calculate for wind do they include rain in the equation? I know it seems like a stupid question that maybe only a physicist could explain but im sure that some of you have enough experience to enlighten me somewhat.
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Old September 18, 2005, 08:21 PM   #2
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I seem to vaguely recall seeing an article somewhere which said the bullet and the raindrop never get together. If I ever understood why that was supposed to be the way it worked, I've forgotten it now. Rewards of geezerhood, I guess.

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Old September 18, 2005, 08:27 PM   #3
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Steve because the bullet is so small and going at such a speed that they wont touch most likly unless your in a big strom ??

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Old September 18, 2005, 08:37 PM   #4
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The air traveling around the projectile forms a dense shield of air which pushes the water away (shields up, Scotty!)

I always wondered if machinegun rounds 'drafted' off of the round in front of them like a Nascar stockcar LOL
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Old September 19, 2005, 08:12 AM   #5
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Buudy and I went shooting in the rain...

Not a hard rain, but big drops...Shootingmostly .22s, it did seem that our groups were larger than normal...Center fires didn't seem to be affected...Not anykind of scientific proof....We discussed this question onthe way home....Would be interesting to seesome scientific results.
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Old September 19, 2005, 08:28 AM   #6
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In my experience shooting in many torrential downpours in the North Carolina Police Combat Pistol League, the accuracy of the weapon is not affected, but your view of the sights can be impaired by the rain on the slide and steam if the gun is hot. We never saw any noticable decrease in scores and we've shot in hurricanes before...
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Old September 19, 2005, 09:49 AM   #7
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Could be crazy if we got rainstorms where huge droplets came down, afterall we're not supposed to shoot the surface of water due to ricochet... what would happen if you could richochet off of a raindrop?
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Old September 19, 2005, 10:24 AM   #8
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Ricochet off a raindrop

(Hah--sounds like a song title from a 1940's musical!)

Seriously--Bullets ricochet off water bodies because the water just can't get out of the way fast enough. I have personally ricochet'd off water, falling off the outside of a water-skiing turn, and it feels just as hard as bouncing and sliding along a gymnasium floor--except for the floor burns! And that was only maybe 50 fps, not hundreds or thousands of fps like a bullet.

Hydrofoil craft work the same way--the foil--and the craft--is moving so fast that the water supports the craft's weight, because the water just can't get out of the way fast enough. When the craft slows down, the foil works less and less well until finally the craft is floating on its regular hull, and moving at the speed of a "regular" boat. As to speed, again a hydrofoil will be moving at less than 100 fps. (88 fps = 60 mph.)

However, in the case of a raindrop, the drop is only about the size of the bullet, or smaller, and there's air on the other side of the drop, not more water, so it has no trouble breaking up and getting out of the way of the bullet. (Air is softer than water, and air is compressible, wheras water is not.) And the air the bullet is pushing to the side helps push the raindrop out of the way, also. You may have stood beside a road on a rainy day and noticed some of the raindrops being pushed aside around the moving cars.

There's another factor: The bullet is moving so much faster than the raindrop that the liklihood of their colliding is very low. In the early part of WWI, machine guns were fired right through the paths of airplane propellors--almost always with no damage to the propellors! because the bullets were moving so much faster.

Bottom line: IMHO, raindrops will not materially affect the flight of bullets.

I have not tested this by going out and target shooting in a downpour, and Lord willing I never will! It would be interesting to read someone ELSE's report who carefully tried this.
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Old September 19, 2005, 10:39 AM   #9
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"In the early part of WWI, machine guns were fired right through the paths of airplane propellors--almost always with no damage to the propellors! because the bullets were moving so much faster."

Well... Actually in the very early days of firing through the propellers, bullets *did* routinely hit them, and the aviators quickly figured out that they needed to do something about it. At first they applied armor to the props, but eventually synchronized their guns to fire at times when the bullets would not hit the prop.

As for rain affecting shooting, I did some math on that once and convinced myself that it's unlikely that a bullet will actually contact a raindrop while in flight, simply because there is so much space between the drops. The bullet travels fast enough that there is almost always a free path for it to follow from muzzle to target. I don't know what happens to the few bullets that *do* manage to hit raindrops, but I know that so far my personal best high power rifle score was fired in *pouring* rain. Maybe there's something Zen-ish going on...

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Old September 19, 2005, 11:04 AM   #10
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I dont understand how, as several of you are saying, that the speed of the bullet will allow for a path to the target free of droplets. Distance between drops etc, I dont understand how this will make chances of an impact void. However, the "envelope" of air around the bullet would (in theory)prevent a drop from actually contacting the bullet. Can someone explain the "clear path theory". I just dont get it.
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Old September 19, 2005, 11:25 AM   #11
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Here's my theory...

Picture the path your bullet will take from muzzle to target. For simplicity, assume it is perfectly straight, rather than curved. This will introduce some error, but not much. Now imagine that you can look down this "tube" during a rainstorm and see how often a raindrop passes through it at some point along its length. For the purposes of discussion, let's just say you see one drop every three seconds.

Now calculate how long it will take for your bullet to travel to the target. Again, just for discussion, let's say it's 100 milliseconds. Your bullet, then, has a three second clear window to travel through in 100 milliseconds. If you fire continuously, about 1 bullet in 30 (3 seconds divided by 100 milliseconds) will contact a raindrop (either by hitting one head-on, or having one fall on it).

It remains to be seen if this occasional contact can cause a 10 to turn into a 9, but...

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Old September 19, 2005, 11:27 AM   #12
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Bullets and things

TimRB--I read that Anthony Fokker, the designer of fighter planes for Germany, used his boyhood experience throwing rocks at windmill blades to figure out that MOST of the machine gun bullets would go right past the aircraft propellor, when the propellor wasn't in the way. (Fokker was Dutch; apparently Dutch boys threw rocks @ windmill blades regularly. Can't say that surprises me any.) Read this years ago, sorry, can't cite a reference.

Yes, once in a while a blade would be hit, and they armored the blades and then synchronized the blade/gun just as you said.

Zeisloft--Consider the whole circle a 2-blade propellor makes. Consider how wide the prop is. At any given moment, The prop blade is likely to be somewhere else in its arc than right in front of the machine gun muzzle. The machine gun bullet, moving much faster than the prop, goes through that unoccupied space.

Or consider the air during a downpour of rain--At any given moment, most of the air does NOT contain a drop of water, even during a heavy rain. So the liklihood of a bullet striking a water droplet is very low--the droplets of rain are almost standing still compared to the bullet.

We tend to think of a downpour as nearly solid water, because (1) we are so much bigger than the drops of rain, and (2) we move so slowly by comparison with the drops.

Bottom line: The smaller you are, and the faster you move, the harder you are to hit.
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Old September 19, 2005, 12:37 PM   #13
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I was just curious if you get a large enough mass of falling water if it's possible in a perfect physics world to get a ricochet... anything is possible in a perfect physics world, it would just be cool

Definately agree with the points made... although if you could somehow devise a strategy to bounce from raindrop to raindrop to deviate the path of a bullet... it would be like the trick shot of a lifetime...
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Old September 19, 2005, 12:49 PM   #14
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I think Tim is onto something with this, so I'll pick the ball up and run with it.

In the line of site that he described, lets say there is water at SOME point along this imaginary tube at all times. Given that bullets travel faster than the speed of sound and reach your target almost instantaneously, barring anything like and air pocket around the bullet it will collide with water at some point in its path.

However, given that the bullet is traveling at 900+ fps with hundreds of foot pounds of pressure, my intuition says that a single water droplet won't affect the bullet's trajectory. Now, raining cats and dogs might affect it....

I have a somewhat related wonder?

Remember in the twilight zone episode with the creature on the wing? If you shot a bullet out a plane window, perpendicular to the directon of the wind, at a target on the wing of the plane, would your bullet travel true to your aim or would it be affected by the wind and be completely blown off course?
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Old September 19, 2005, 01:21 PM   #15
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"If you shot a bullet out a plane window, perpendicular to the directon of the wind, at a target on the wing of the plane, would your bullet travel true to your aim or would it be affected by the wind and be completely blown off course?"

If you were shooting at a target on the wing of your own plane, the bullet would think it was travelling through a 100 mph (or whatever) crosswind. If you were travelling in vacuum, then it would fly straight to the target, but then your airplane wouldn't work. Go figure.

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Old September 1, 2013, 10:41 PM   #16
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Yes and no

A vortex is surrounding the projectile while in supersonic flight so the actual rain drops will never come into direct contact with the bullet. However, the trajectory will change due to the atmospheric conditions. The density altitude will be different when its raining then it would be on a clear day. Therefore the rain will affect the bullet but not by direct contact.
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Old September 1, 2013, 11:29 PM   #17
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Dunno how it affects accuracy (I was a young hooligan more interested in shooting a lot than shooting well) but I know the shock wave of a passing bullet can make water condense out the air- on a foggy/ drizzly day, we were shooting rifles in a pasture, and the bullets appeared to make contrails of fog ....
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Old September 2, 2013, 12:30 AM   #18
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The question was asked in the context of a sniper. If we're talking shots of 1,000 yards or more, I'm going to say heavy rains may affect the shot.

Rapid change in humidity, turbulent crosswinds (maybe changing direction many times), change in temperature change in air pressure. In Florida, we can have rain in a 100 yard patch and then no rain on either side of it

But I doubt an actual drop of water does much.
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Old September 2, 2013, 02:06 AM   #19
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What about a subsonic bullet being fired at targets that are 500-600 meters away?
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Old September 2, 2013, 03:40 PM   #20
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The idea that you could make a .3 inch diameter tube and run it 100 yards in a decent rainstorm it isn't going to be hit by rain almost constantly seems absurd to me. No way for 5-600 yards.

Even if there is a compressed air "shield" around the bullet, when that "shield" hits a incompressible heavier than air water droplet the air compression in that area will increase. This will result in a force against the bullet. So, even with the compressed air buffer, I think there will still be a force on the bullet. Probably reduced.

Given the period of time the effect will be present, milliseconds at most, the effect is likely negligible up until the bullet drops through the sound barrier. At that point the turbulence from passing the sound barrier probably makes the water droplet effects irrelevant. A bullet that is subsonic to begin with isn't going to be shot at that long of a range.

No matter the science, the consensus seems to be the effect is negligible.
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Old September 2, 2013, 06:37 PM   #21
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Quote:
A bullet that is subsonic to begin with isn't going to be shot at that long of a range.
I would have to argue against that. The VSS sniper rifle had an effective range of 500-600 meters with a 9x39 subsonic bullet. A .338 whisper with a 300 grain boat tail has about the same amount of drop and time of flight at 500 yards that a .30-06 has at 1000 yards. With only about 16 inches of wind drift in a 10mph 90 degree crosswind, and has only lost about 120fps of velocity at that range.
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Old September 2, 2013, 07:15 PM   #22
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Quote:
A vortex is surrounding the projectile while in supersonic flight so the actual rain drops will never come into direct contact with the bullet.
There's probably some truth to this in the sense that a drop won't "fall" onto a bullet due to the air disturbance around the projectile. However, a bullet could definitely run into the "side" of a rain drop and that would almost certainly affect the trajectory in some manner.
Quote:
I read that Anthony Fokker, the designer of fighter planes for Germany, used his boyhood experience throwing rocks at windmill blades to figure out that MOST of the machine gun bullets would go right past the aircraft propellor, when the propellor wasn't in the way. (Fokker was Dutch; apparently Dutch boys threw rocks @ windmill blades regularly.
Fokker was credited with devising the synchronising method that basically prevented the gun from firing if a propellor blade was in front of the muzzle. The first person to shoot a gun through the propellor arc was Roland Garros, a French pilot on the Allied side and he did the calculations to determine that most of the bullets would miss the blades. He also armored the back of the blades to deflect the few hits that would occur.

When Garros' plane was shot down over Germany, they realized what he had been doing and Fokker claimed to have improved on the basic idea with the interruptor device. Turns out that there were patents for similar mechanisms dating back before Garros' shootdown indicating that Fokker probably didn't come up with the design as he claimed he did.
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Old September 2, 2013, 07:21 PM   #23
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" Would the rain change the bullets trajectory after hitting a raindrop or does it just go so fast that it doesnt hit the rain?"

in my opinion a bullet can travel fast enough to not hit a raindrop, however the likely hood of the bullet(including the air cushion around the bullet) colliding with a raindrop within the trajectory of a long distance shot is high. now when such an event occurs, there will be an effect. the question isn't as stated, but rather how much of an effect, just because we can't measure the effect doesn't mean that it did not happen. honestly it would take thousands of rounds, thousands of high speed cameras, and a really expensive sprinkler system to test the ideas contained in this thread.
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Old September 2, 2013, 09:24 PM   #24
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JD0x0, I was thinking about 600 yards would be the max someone would shoot a subsonic bullet with any hope of precision and that would be inside the range most hypersonic rounds drop below the sound barrier. The low end of range where common hypersonic rounds break the sound barrier is about 450 yards. 30-06 is around 1000, 223 is about 800 yards, and X39 is about 600. I calculated theoretical values for a few rounds about 5 years ago. I can't remember exactly, but I think something broke between 450 and 500 yards.

If you are shooting 1000 yards and the bullet hits a drop of rain one inch out the muzzle, it might have a negligible, but measurable, effect at 1000 yards. Not only would the rounds trajectory be pushed creating a linear effect, but the bullet might start to destabilize which would result in an exponential effect on accuracy. For it to be a problem I am guessing the destabilization must occur having the exponential effect. The destabilization might increase drag and reduce the range the bullet transitions to subsonic creating further problems. If my thought on that are correct the effect will be much more than twice as pronounced at twice the range. At 5-600 yards I don't see much of a possibility of there being a consistent measurable effect no matter how expensive a sprinkler one buys for the experiment.

Some info/thoughts on the sound barrier effects:
http://www.chuckhawks.com/rifle_ballistics_table.htm Hardly anything modern just over the barrier.
http://www.marlinowners.com/forum/45...es-bullet.html
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Old September 3, 2013, 10:49 AM   #25
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I used to hear guys talking about their hopped up 22-250 or .220 Swift blowing up bullets occasionally when they shot in a heavy rainstorm.

I suppose it is possible but I don't think it would be very likely.

I have shot light bullets pretty fast when prone in a wheat stubble field and seeing what looked like an explosion 100 yards out or so. I think it was either the bullet coming apart or the bullet hit some wheat stubble and blew up. I was shooting at some coyotes and never saw a bullet strike anywhere near them.
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