The Effect a Raindrop Has On a Bullet

[A.T.]

This is only strictly true for the water which lies in the plane- a lot will be deflected outwards of the paper/screen, and the same amount will be deflected inwards towards the screen. Although these two z-direction impulses cancel, you are counting them in your calculation.

Yes I mentioned the spraying.

I think the effective angle will be much smaller,

45° was just an example. Also note that we assume perfectly inelastic collision. If the water bounces off then the effective angle is different from the shape of the bullet.

If your mass ratio is 1/100 then assuming the bullet weight is about 5 g, the raindrop radius must be about 2.5 mm, whereas the bullet radius is about 3.8 mm. They're pretty similar in size and that makes me think this overestimate is quite big.

That is a good point. I think most of the effect could come from destablisation/precession, rather than from direct momentum transfer. But that is even more difficult to estimate.

 

[A.T.]

As shown before, the bullet speed cancels in the equations if it has to push water away with its conical section.

An intuitive reason that the transferred momentum cannot depend on the momentum ratio or the speed ratio is that the those ratios are frame dependent, while the transferred momentum is absolute. The transferred momentum can only depend on other frame invariant variables like the mass ratio.

 

[Andrew Mason]

If you're talking about a cue ball striking another at 45 degrees and suffering a noticeable traverse deflection I'd agree- the mass ratio of a raindrop to a bullet could easily be big enough to give a noticeable (~cm) deflection over a path of 350 m. However, the bullet is not a sphere and the raindrop is not rigid, so I don't think you'll get anywhere near that deflection. Most likely the bullet will glance the droplet, and only a small fraction of water will deflect sideways, with most of it being pushed forwards.

I tend to agree. But the "sideways" is not all the same direction. It would be all around the bullet so it would not prefer one "sideways" direction over the other.

As shown before, the bullet speed cancels in the equations if it has to push water away with its conical section.

The bullet has to push the rain drop away with that force (12N? Does not matter!) in order to proceed in its approximate path.

I agree that the bullet has to push away whatever is in its path. Whether it pushes the entire raindrop depends on whether it hits the entire raindrop. If the 6.5 mm bullet hits the entire 6mm diameter raindrop it will have to explode practically through the middle of it. In that case it is only the momentum of the raindrop before the collision that would affect the lateral momentum of the bullet.

So what you are suggesting is that the bullet just hits half the raindrop with half a bullet.

Analysing that is a bit more complicated. You are suggesting that it imparts momentum to the raindrop to one side of the bullet's path and the bullet experiences a net sideways momentum that is equal to the mass of the raindrop x a very high speed, which is sufficient to change the path of the bullet significantly.

I don't see that. I would expect that what happens is that it imparts momentum to the molecules comprising the part of the drop that it passes through over a range of angles from 0-180 degrees around one side of the bullet. It is the sum of all those momenta that imparts a net momentum to the bullet. And it will not all be sideways - much of it will be forward momentum. So it is only a small portion of the part of the raindrop that the bullet passes through that imparts much net lateral momentum to the bullet.

I expect the physics would be complicated to analyse accurately. The American Rifleman article that I referred to earlier shows the results of an experiment firing rifle bullets at wood dowels at 25 yards and observing the bullet orientation and path over the ensuing 75 yards using 32 paper screens. The paths of the bullets was spiral, a consequence of the loss of stability rather than lateral momentum imparted by the contact with the dowel. Some of the tests involved striking just the edge of the dowel (see Fig. 9 from the article). This caused a deflection of about 9 inches over 75 yards.

I just can't see a single raindrop having nearly as much effect as a hardwood dowel.

AM

 

[mfb]

So what you are suggesting is that the bullet just hits half the raindrop with half a bullet.

My calculations assumed a raindrop diameter of ~3mm, hitting one side of the bullet. I expect that sidewards deflection reduces the maximal net momentum by about 20-30% (if the drop covers exactly "one side" of the bullet in a uniform way, it would be a factor of 2/pi or a reduction by 36%).

much of it will be forward momentum

That does not matter, see A.T.'s sketch.

I expect the physics would be complicated to analyse accurately.

That's why I calculated a rough estimate, not a precise number.

I don't see how figure 9 corresponds to an asymmetric hit. At that speed, wood and water are not so different, if their area density is similar.

 

[Win_94]

The paths of the bullets was spiral, a consequence of the loss of stability rather than lateral momentum imparted by the contact with the dowel. Some of the tests involved striking just the edge of the dowel (see Fig. 9 from the article). This caused a deflection of about 9 inches over 75 yards.

I just can't see a single raindrop having nearly as much effect as a hardwood dowel.

AM

I'm seeing at the most, 8 inches of deviation at 260 yards; 1/4 of the dowels deviation at most, and 1/12 of the dowels deviation on average.

Oh, from viewing the bullet trace, I don't notice any spiral affect.

 

[Andrew Mason]

I'm seeing at the most, 8 inches of deviation at 260 yards; 1/4 of the dowels deviation at most, and 1/12 of the dowels deviation on average.

Oh, from viewing the bullet trace, I don't notice any spiral affect.

Perhaps you could describe how you are conducting your experiments and how you are determining the deviation.

One way to do this would be to see how much a small vertical stream of water deflects a bullet. In other words, do the same experiments as the American Rifleman did but substituting a water stream for the dowel.

AM

 

[Win_94]

Perhaps you could describe how you are conducting your experiments and how you are determining the deviation.

One way to do this would be to see how much a small vertical stream of water deflects a bullet. In other words, do the same experiments as the American Rifleman did but substituting a water stream for the dowel.

AM

The experiment is outlined in Post 12.

Here is a video of the test. Water Droplet POI Shift Test
Here is a follow-up video to see the droplet hits better. Zoomed In, Slow Motion, Water Drop Hits

I created a dropper devise as to shoot through a stream of drops. I wanted to preform the test in a round robin method but my devise was freezing-up on the first 4 of 10 shots. So the last 6 shots I set out to hit water.

I don't have a gun vise so I preformed the test as I would usually shoot. the first 4 shots at 300 yards made a 3.25 inch group, (the 4th shot was a called flier, the first 3 shots were what I would expect, a 1.25 inch group at 300 yards.) I was confident on on the technical aspects of all the shots except shot 4. I was shooting a 30-06 using ball ammo, (fill metal jacket bullets,) per my own hand-loaded cartridges. The velocity was 2600fps at the muzzle, with an estimated 2500fps at the dropper devise.

The dropper devise was set 40 yards forward of the muzzle to insure muzzle blast could not skew the test. So the bullets would travel 260 yards before hitting the target.

The temperature was 15ºF at dawn, when the test was over, (approximately 2 hours later,) the temperature was 21ºF. Ammo can be adversely affected by large temperature swings; a 6ºF difference would not skew the test.

The wind did change during the test. At first there was a 6mph wind from 10 0'clock, resulting in a 4 inch deviation to the right. As the day went on the winds got a bit stronger but mainly from 12 o'clock. Wind has a horizontal element, a light to moderate wind from 12 o'clock will affect the bullets trajectory minimally. You can see three different wind flag positions as to estimate if wind had an affect on the point of impact.

I tried to get a trusted marksman to preform the experiment but they are not going to go against the grain of common belief. Firearm enthusiast are a strange crowd, if they were wrong about an issue they have been vocal about for years, it would call their expertise into question.
Case in point, I suspect Adam Ant is from a firearms site which I raised the issue at first. I assume they Googled the quote I posted from Drakkith, and came here to disrupt the conversation.
This is why I don't link to here, because it will turn it into a melee.
[edit]On viewing of Adam's profile... He joined before the my post was created, so he isn't from that firearms site; but he is showing the bias of firearms enthusiasts. It is common belief that the laws of physics apply to all firearms and associated cartridges, except for the lever action 30-30.[/edit]

I also have a video displaying the energy of a shockwave. Shockwave Energy Test
I figured if a shockwave could vaporize a raindrop before the bullet could hit it, it should shred a wet napkin, (which is the most delicate thing I could imagine.)
This page display a good picture of a bullet bow shockwave.
Here is a good video of one.


I have contacted a YouTube channel with a high speed camera to record a bullet hitting a raindrop. Unfortunately the video will not be recorded until the cold weather breaks in New England.

If there are any more questions, I would be glad to answer them.

Thank you for all the efforts, all of you have contributed!

 

[Andrew Mason]

I created a dropper devise as to shoot through a stream of drops. I wanted to preform the test in a round robin method but my devise was freezing-up on the first 4 of 10 shots. So the last 6 shots I set out to hit water.

I don't have a gun vise so I preformed the test as I would usually shoot. the first 4 shots at 300 yards made a 3.25 inch group, (the 4th shot was a called flier, the first 3 shots were what I would expect, a 1.25 inch group at 300 yards.) I was confident on on the technical aspects of all the shots except shot 4. I was shooting a 30-06 using ball ammo, (fill metal jacket bullets,) per my own hand-loaded cartridges. The velocity was 2600fps at the muzzle, with an estimated 2500fps at the dropper devise.

Unless you can compare the trajectory prior to striking the water to the trajectory after, it is impossible to tell whether a shot was deflected. The distribution of shots at the target with the water off appears to be comparable to the spread of shots through the water. Even if there was some significant difference to the distribution, that difference could be the result of other factors since you are relying on just your aim.

You might try using the paper screen technique used by Mr. Moore in the American Rifleman article.
AM

 

[Win_94]

Unless you can compare the trajectory prior to striking the water to the trajectory after, it is impossible to tell whether a shot was deflected. The distribution of shots at the target with the water off appears to be comparable to the spread of shots through the water. Even if there was some significant difference to the distribution, that difference could be the result of other factors since you are relying on just your aim.

You might try using the paper screen technique used by Mr. Moore in the American Rifleman article.
AM

There is no way I could see the target with paper in the way.

The 4 shots I took without hitting water, including the flier is more accurate than the 5 shot group in the test you've provided. If their group was shot at 300 yards it would have been 5.1 inches as opposed to my 3.25 inches. My rifle is more accurate even when I screw-up.

That is the problem with m doing these tests, no one will ever believe the results. No matter what I do.
I wasted 10 shots on that test and am not able to buy more ammo. There is no ammo to be had. That is the only test on the planet on this subject; you're saying it is completely irrelevant?
Even when I shoot cartridges with varying charge weights, the dispersion isn't 12 inches.
I don't have a budget on this project to buy equipment as you you deem necessary. I shot my last 10 rounds of the same load components. I can't preform another test, and no one else on the planet will touch it.

 

[Win_94]

The distribution of shots at the target with the water off appears to be comparable to the spread of shots through the water.

No. The 4 shot group that didn't touch water are 1/4 the size of those that hit water.

 

[Win_94]

Unless you can compare the trajectory prior to striking the water to the trajectory after, it is impossible to tell whether a shot was deflected.

That is also wrong. You are assuming the bullets striking the water will tumble and corkscrew to the target, I don't think it will happen, and it isn't happening. If it were happening there would be sideways strikes on the target; there are none.
I think the strike on a liquid, can't be half as violent as a hit on a solid. You can't assume the same corkscrew results.

 

[mikeph]

A few things I'm not clear on, how can you tell the bullet is hitting water? I don't see any splatter on the videos, and I'd assume the water gets vaporised anyway.

 

[Win_94]

A few things I'm not clear on, how can you tell the bullet is hitting water? I don't see any splatter on the videos, and I'd assume the water gets vaporised anyway.

Some turned into vapor, some were splatter. I assume vapor is more of a center hit than the splatter. I'm working on another post as to attempt another test. The new test will be using another camera as to capture the water hit more clearly. Please be patient.

 

[OmCheeto]

There is no way I could see the target with paper in the way.

The 4 shots I took without hitting water, including the flier is more accurate than the 5 shot group in the test you've provided. If their group was shot at 300 yards it would have been 5.1 inches as opposed to my 3.25 inches. My rifle is more accurate even when I screw-up.

That is the problem with m doing these tests, no one will ever believe the results. No matter what I do.
I wasted 10 shots on that test and am not able to buy more ammo. There is no ammo to be had. That is the only test on the planet on this subject; you're saying it is completely irrelevant?
Even when I shoot cartridges with varying charge weights, the dispersion isn't 12 inches.



I don't have a budget on this project to buy equipment as you you deem necessary. I shot the last 10 rounds that I had, which are of the same load components. I can't preform another test, and no one else on the planet will touch it.

I would do the test, if I had a rifle, and the conditions you have. Unfortunately it is not likely to be below freezing in my area for another 8 months.

I don't have much of a budget either, but I never let that stop me from doing science experiments.

First off, the raindrops velocity, compared to that of the bullets, can be effectively modeled as zero. Secondly, the raindrop probably appears to be solid from the bullets point of view, as pointed out by jim mcnamara in post #19: 740 m/s = 1655 mph.

If you can find, or make more bullets, I would perform the following experiment:

Supplies needed
1. powdered graphite
2. a bunch of paper
3. a roll of duct tape
4. an old ice cube tray
5. bullets
6. toothpicks
7. an eye dropper
8. pencil
9. clipboard
10. tape measure

Setup:
1. put a bit of powdered graphite into each of the old ice cube trays cavities
2. in the first cavity, place one drop of water, in the second cavity, place two drops of water, continue as in this manner with all cavities.
3. stir graphite with toothpick
4. leave a toothpick in each cavity
5. stick ice cube tray in freezer, making sure toothpicks are in the center of each cavity, and will make a wonderful graphite popsicle stick thing for tomorrow morning.
6. set up a linear paper wall, one foot away and parallel to the bullets paths, 11" high x 56" wide, with an old piece of plywood and duct tape 5 feet in front of where you are firing from
7. set up a paper wall with an old piece of plywood and duct tape 250 yards away. Same dimensions as above.
8. set up a stand between your gun and the paper wall nearest you that will hold steady your toothpick-graphite-sicles, that is in line with your target paper wall.

Experiment:
1. go out when it is still below freezing the next morning, as otherwise your graphitesicles will melt.
2. get another piece of paper on a clipboard, create a matrix of drops per graphitesicle,

Drops_____LOGD____DOBFB
1__________8"_____3"
2__________9"_____4"
3_________10"_____5"
etc
*LOGD = Length Of Graphitesicle Dispersion Pattern
*DOBDFB = Displacement Of Bullet From Bullseye

3. align the graphitesicles, such that they will be glanced by the bullets you are firing at the target
4. after each shot, circle the graphite marks on the near paper wall. Measure the length of the track with your tape measure. Write down the length in column 2.
5. after each shot, circle the bullet hole at the target with your pencil. Measure the distance from the bullseye. Write down that distance in column 3.

Modifications to experiment:
1. after each firing, change the paper on the near paper wall. It may be difficult to distinguish subsequent splatter patterns.


Assumptions on my part:
1. I theorize, that the graphitesicles will turn into water vapor once struck by the bullet, due to the tremendous pressure.
2. The graphite will adhere to the near paper wall. (Perhaps use paper towels, rather than notebook paper)
3. You'll be able to come up with more bullets.



When complete, show us your results.

ps. This very much reminds me of how I once metaphorically described high energy particle physics to someone.

Take a Colt 45, shoot a watermelon, and have three blind men interpret what the watermelon consisted of by having the blind men feel around for seeds, goopy stuff, and outer shell bits.

 

[mfb]

That is an interesting approach.

Here is a simpler version of the experiment:
Create a thin stream of water, which fractures into individual drops quickly. Shoot through the point where you have a high drop density. Check that you can produce this in a reliable way (camera?) and switch it on/off.

Shoot n times without water, ~2n times with water, repeat.
For each set of shots, record the 2-dimensional positions of the impacts. Choose n to have very similar conditions for both shot types, but probably large enough such that you don't have to run to the target after every shot.

Post the raw data here.
The shots with water should have two components: One with the same distribution as the shots without water (no drop hit) and one component which is broader than the other (by some unknown amount) as it has the additional water deflection. I don't know how expensive those bullets are, so it might be impossible to see this splitting, but at least you can check the average deviation and something like the amount of outliers.

 

[Win_94]

I looked over my stocks and I can disassemble 14 30-30 cartridges, to make 10 30-06 cartridges of the same load as the previous test.

Before I preform another test, I want the parameters laid-out.

First; I'll hook up the dropper device to a hose at the house; so the range will be 200 yards this time.
I need to do this because when I pulled shot 4, it was due to rushing to get the shot off before the water ran out.
At that time, I decided to change my procedure as to not need to rush.

Second; I'll position the camera in such a way to capture the bullet hits on the water more clearly. I'll have a dark background with lighting on the water drops.
(This is the reason I am preforming another test, because the video quality was not good enough to be clear enough after the 2 edits needed to make the video, then upload it to YouTube.)
I only have one camera, the video of the water hits will be the only video.

Third; I'll use a large piece of cardboard as the target, so all bullet hits can be examined to see if there is a pronounced yawing affect. This will also aid in exact measurements since there will be no complete misses, (as with shot number 5.)

Fourth; on the issue of having paper at specific intervals.
The only way I could make that work, is to make a free recoil devise to cradle my rifle. See this video...

...and then I would need to make a concrete bench to rig the devise to.
That is the only way to insure the rifle is still on a relatively close aiming point without manually aiming each time.
I don't have either of those items.

Another issue with the paper is I have rolling hills on my range, I would need at least 32 12 foot poles and as many shorter ones to position paper at 32 specific areas to capture the bullet trajectories on the range I have chosen to shoot at. I could reduce the length to 100 yards, but then I would need to use the bottle to feed the dropper devise since it is not close enough to the house. If I use the bottle, I am sure it will cause me to rush again, resulting in another flier, and again, a completely worthless test. That is not happen this time.

The paper at intervals is not needed; the point of impacts of the shots not hitting water should suffice as a the norm. We need not know if yaw or deflection was the result of the deviation, we simply need to know if there is deviation.

Fifth; I am going to take the shots off of a bench in such a way that I get exceptional accuracy; since there is a hose fed dropper devise, I will not need to rush, therefore all shots will go as planned.
I'll shoot through water first; this way if I miss water, I can make up for it later down the road. When I know I've hit water 5 times, I'll then shoot the rest of the 10 shots without water.

Sixth; The measurement of all shots not hitting water determine the norm. The measurement of all shots hitting water will be weighed relative to the norm. Anything else is ridiculous! My shooting ability with the shots that didn't hit water in the first test, was more precise than American Rifleman's mechanical devise.

Seventh; if there is any other elements of the test that absolutely needs to be included, or there is anything in my proposed test that is unacceptable, speak-up now.

 

[Win_94]

I would do the test, if I had a rifle, and the conditions you have. Unfortunately it is not likely to be below freezing in my area for another 8 months.

I don't have much of a budget either, but I never let that stop me from doing science experiments.

First off, the raindrops velocity, compared to that of the bullets, can be effectively modeled as zero. Secondly, the raindrop probably appears to be solid from the bullets point of view, as pointed out by jim mcnamara in post #19: 740 m/s = 1655 mph.

If you can find, or make more bullets, I would perform the following experiment:

Supplies needed
1. powdered graphite
2. a bunch of paper
3. a roll of duct tape
4. an old ice cube tray
5. bullets
6. toothpicks
7. an eye dropper
8. pencil
9. clipboard
10. tape measure

Setup:
1. put a bit of powdered graphite into each of the old ice cube trays cavities
2. in the first cavity, place one drop of water, in the second cavity, place two drops of water, continue as in this manner with all cavities.
3. stir graphite with toothpick
4. leave a toothpick in each cavity
5. stick ice cube tray in freezer, making sure toothpicks are in the center of each cavity, and will make a wonderful graphite popsicle stick thing for tomorrow morning.
6. set up a linear paper wall, one foot away and parallel to the bullets paths, 11" high x 56" wide, with an old piece of plywood and duct tape 5 feet in front of where you are firing from
7. set up a paper wall with an old piece of plywood and duct tape 250 yards away. Same dimensions as above.
8. set up a stand between your gun and the paper wall nearest you that will hold steady your toothpick-graphite-sicles, that is in line with your target paper wall.

Experiment:
1. go out when it is still below freezing the next morning, as otherwise your graphitesicles will melt.
2. get another piece of paper on a clipboard, create a matrix of drops per graphitesicle,

Drops_____LOGD____DOBFB
1__________8"_____3"
2__________9"_____4"
3_________10"_____5"
etc
*LOGD = Length Of Graphitesicle Dispersion Pattern
*DOBDFB = Displacement Of Bullet From Bullseye

3. align the graphitesicles, such that they will be glanced by the bullets you are firing at the target
4. after each shot, circle the graphite marks on the near paper wall. Measure the length of the track with your tape measure. Write down the length in column 2.
5. after each shot, circle the bullet hole at the target with your pencil. Measure the distance from the bullseye. Write down that distance in column 3.

Modifications to experiment:
1. after each firing, change the paper on the near paper wall. It may be difficult to distinguish subsequent splatter patterns.


Assumptions on my part:
1. I theorize, that the graphitesicles will turn into water vapor once struck by the bullet, due to the tremendous pressure.
2. The graphite will adhere to the near paper wall. (Perhaps use paper towels, rather than notebook paper)
3. You'll be able to come up with more bullets.



When complete, show us your results.

ps. This very much reminds me of how I once metaphorically described high energy particle physics to someone.

Ice would skew the test. No one would doubt that ice causes a deviation.

 

[Win_94]

That is an interesting approach.

Here is a simpler version of the experiment:
Create a thin stream of water, which fractures into individual drops quickly. Shoot through the point where you have a high drop density. Check that you can produce this in a reliable way (camera?) and switch it on/off.

The reason I have a lot of drops is because the wind blows the drops quite a lot. ven with the 10 holes I had to shift the rifle left and right to chase the drops insuring to get a hit.

Shoot n times without water, ~2n times with water, repeat.
For each set of shots, record the 2-dimensional positions of the impacts. Choose n to have very similar conditions for both shot types, but probably large enough such that you don't have to run to the target after every shot.

I was going to do it that way, but was missing the drops due to the stream being too sparse.
But, The only conditions that would make a difference, would be wind, and that would only deviate side to side. Any differences in height, will be due to drop deflection.

The shots with water should have two components: One with the same distribution as the shots without water (no drop hit) and one component which is broader than the other (by some unknown amount) as it has the additional water deflection. I don't know how expensive those bullets are, so it might be impossible to see this splitting, but at least you can check the average deviation and something like the amount of outliers.

I'm not quite sure what you are saying here. I'll take a stab at addressing it.

Hopefully, I have figured out how fast the flow should be as to be able to hit a drop each time I want to. If I don't have that understood, I might only get 4 or even 3 hits on water; resulting in a skewed test. But this time I'll be close enough to the house to view the video on the computer, I'll probably not be able to see on the camera viewer, I couldn't see them before.
Conditions are not going to be exact, no matter what I do. That is why it needs to be taken into account the condition that will make the largest difference, wind; and that will be a lateral deviation.

It isn't that bullets are expensive, it is that Obama's war on firearms has caused a run on everything firearms. I can't find components anywhere, and when an online store gets them in stock, within minutes they are gone again. I don't expect to be able to buy bullets for months, quite possibly longer.

 

[Win_94]

We need not know if yaw or deflection was the result of the deviation, we simply need to know if there is deviation.

That I've thought about it more... I think yaw must be present. The only way it couldn't be present is if the drop deflected the bullet at a precise balance point. Unless it is a head-on collision, that isn't possible.
I suspect the yaw was slight and was dampened well before it hit the target.

 

[Dale]

One way to do this would be to see how much a small vertical stream of water deflects a bullet. In other words, do the same experiments as the American Rifleman did but substituting a water stream for the dowel.

This would be an awesome Mythbuster's episode. Especially with the high speed camera.

 

[mfb]

This would be an awesome Mythbuster's episode. Especially with the high speed camera.

Thanks, I forgot that in my post.

I'm not quite sure what you are saying here.

See attachment. Paint, yeah :D.

 

[OmCheeto]

Ice would skew the test. No one would doubt that ice causes a deviation.

Ok. How about Jello drops?

 

[Win_94]

Ok. How about Jello drops?

I don't perceive having a problem hitting drops anymore. I hit 6 of 6 the last time, after the flow was accelerated.
But I would like to shoot the drops first to ensure I have at least 5 hits on water.

Besides, when shooting at close range, the scope doesn't get a clear picture on the target. and I would need to shoot at a smaller target than an inch wide stream of water. Then there is the issue of scope being 1.75 inches above the bore, if I adjust the scope to hit the jello at 20 yards, (what I intend the stream to be at this time around,) the point of impact at the target will be unknown. I'd need sighting shots, which would waste shots and I do not have the bullets to waste.

Usually dawn is the calmest time of day windage wise; If I shoot the drops first, the probability of wind widening the drop's dispersion will be minimal. I think that is the way to go.

This would be an awesome Mythbuster's episode. Especially with the high speed camera.

I contacted them about the Understanding Momentum Conservation in Isolated Systems/Gun Recoil vs POI issue I was interested in. It must have not been sexy enough, because they never got back to me.

 

[Win_94]

See attachment. Paint, yeah :D.

I don't know if you're messing with me or what. I have no idea what that means.

 

[Win_94]

Another thing, the point of aim must be constant. The first test had the same point of aim even though I intended to hold for wind; which I understand now would have been a mistake.

So either viewing the wind flags will need to be part of the video, so one can see how the wind is affecting the shots; or only the size of the groups should be taken into account.
In other words, noting the water impact's proximity to that of the non water hits, would be irrelevant due to the probability of differing conditions.

A 10mph wind from 9 o'clock at 200 yards drifts 3.8 inches. That is about the same drift as the 6mph wind from 10 o'clock in the earlier 300 yard test. So wind at 200 yards is greatly reduced, but still a factor.

 

[OmCheeto]

I don't know if you're messing with me or what. I have no idea what that means.

He's not messing with you. His laugh was at himself.
"Paint" is the poor mans doodle tool for PC's.
Many turn their noses up at it.
I use the mac version.

His doodle is a graphical representation of the target area experiment I described.
The more water the bullet comes in contact, uni-laterally, the larger the deflection.

 

[Win_94]

He's not messing with you. His laugh was at himself.
"Paint" is the poor mans doodle tool for PC's.
Many turn their noses up at it.
I use the mac version.

Yes I get the "paint" reference; I just didn't understand the drawing.

His doodle is a graphical representation of the target area experiment I described.
The more water the bullet comes in contact, uni-laterally, the larger the deflection.

Ok, I understand what he means now... but trying to hit a single drop is what I need to try for. Because even in a heavy rain, the odds of hitting a single drop is great.
So are you implying that I need to hit more water than one drop? A single drop hit, two at the most is what I need to attempt for the experiment to be consistent with moderate to heavy rain shooting conditions.

I'm confident I'll hit the drops I need to.

 

[Aero51]

From an aerodynamics stand point there are a few things to take into account

1) The raindrops do not change the macroscopic shape of the projectile
2) They will "wet" the surface with a microfilm of drops and water
3) The mass of the bullet will increase slightly

These three properties lead me to the following conclusions:

1) The form drag and induced drag will not be changed. In other words, drag due to separation of the air from the surface of the body and drag due to lift created by the body will not be affected by the rain.

2) If the mass increase is non-negligible, then the rate of rotation of the bullet will decrease proportionality to conserve angular momentum. This will decrease the overall accuracy and stability of the bullet.

3)This leads me to the conclusion that the raindrop and moist air will increase the skin friction coefficient of the bullet (or drag due to the air shearing over the surface) and result in a lower average velocity and a decrease in trajectory.

 

[mfb]

@Win_94: A single drop hit is fine, and I don't see where multiple hits were mentioned here. What my graph is describing: Not all tests "with water" will hit a drop, so you have some shots without a hit (giving a narrow cluster of impacts at the target) and some with (giving a broader distribution).
I am not really convinced that the camera can accurately see the hits, so it is good if the study can give results even without that information.

 

[mikeph]

A tracer round in low light with a long shutter speed camera placed behind the gun might capture it. E.g. if the bullet is deflected downwards, a camera positioned at the same height but ~1m to the left/right of the gun should give you an angled trajectory. Might be tricky to get a deep enough depth of field.mfb- I don't see how the distribution approach will work, hitting the water is not binary, some bullets may glance a droplet and be slightly deflected, and those glancing bullets will form a distribution with an intermediate half-width.