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doghunter
10-11-2015, 07:01 AM
G'day.

When shooting on a rainy day, what is the affect on a projectile when it hits a raindrop?

* doghunter *

dk hunt 14
10-11-2015, 09:08 AM
I don't believe it hurts anything. I have seen some of the best groups ever fired in 1000 yard BR in the rain. If it would hurt it surely would show up there. Matt

B.Larson
10-11-2015, 09:34 AM
I don't believe it hurts anything. I have seen some of the best groups ever fired in 1000 yard BR in the rain. If it would hurt it surely would show up there. Matt

I HAVE HAD THE SAME OUTCOME AS MATT........ bullet never hits a drop.....cause of the air wake in front of it.....

Wilbur
10-11-2015, 10:47 AM
I had a math whiz do some calculating some years ago and he determined that in a light rain a bullet would have little chance of hitting a rain drop. Certainly, the harder the rain, the greater the chance.

You will know when your bullet hits a raindrop. It makes a clean, ragged hole not necessarily where you wanted said hole to be.

If it's raining, ALWAYS put a drizzle deflector such that the roof doesn't drip in your line of fire. You probably won't do this until you see the results but don't say I didn't tell you so.

coyotechet
10-11-2015, 11:29 AM
I shot the NBRSA Natís at Kelblyís around 2003/2004 in a heavy rain, on that relay of 60 shooterís shooting at 200 yds there were more groups over 2 inches then under and very few of the groups where under 1 inch. Heavy Rain and 6PPC donít mix well for group shooting.
Chet

Dusty Stevens
10-11-2015, 11:51 AM
It throws them way out!

mwezell
10-11-2015, 11:51 AM
I had a math whiz do some calculating some years ago and he determined that in a light rain a bullet would have little chance if hitting a rain drop. Certainly, the harder the rain, the greater the chance.

You will know when your bullet hits a raindrop. It makes a clean, ragged hole not necessarily where you wanted said hole to be.

If it's raining, ALWAYS put a drizzle deflector such that the roof doesn't drip in your line of fire. You probably won't do this until you see the results but don't say I didn't tell you so.

Right! I had this happen to me a few years back in a $1000 money shoot. Rain was coming down in buckets, flags were motionless, gun was driving nails at 300 yards...until...

I was in the running to win the money when I had a shot drop several(?) rings low and just a tad right or left..I can't recall which. To this day, I say it was water coming from the front edge of the roof that did it. Of course, it could have been a number of things, but never had it happen like that before or since. Oh well....I make very sure to be cognizant of it now.

Wilbur
10-11-2015, 12:02 PM
About the only thing you can do is make sure you don't shot through a stream running off the roof. Beyond that there's nothing you can do but shoot and hope.

dk hunt 14
10-11-2015, 12:49 PM
I have never seen this happen. But we shoot a lot bigger bullets and faster twists. If it rains too hard we can't shoot because we can't see at 1000 yards. I believe when it rains lightly the better groups come because we can see a lot clearer and usually no mirage. And usually the winds settle and hold. At longrange they both can hurt you some. Matt

brickeyee
10-11-2015, 07:47 PM
A raindrop is not going to get past the Mach wave attached to the front of a supersonic bullet.

Dusty Stevens
10-11-2015, 09:50 PM
I shot the NBRSA Natís at Kelblyís around 2003/2004 in a heavy rain, on that relay of 60 shooterís shooting at 200 yds there were more groups over 2 inches then under and very few of the groups where under 1 inch. Heavy Rain and 6PPC donít mix well for group shooting.
Chet

I see it every time it rains bad. I guess the rain affects the mach wave more at 3400fps than 2950

mks
10-11-2015, 10:37 PM
Dťjŗ vue all over again:

http://benchrest.com/showthread.php?63960-Shooting-in-the-rain

Andy Cross
10-12-2015, 03:22 AM
A raindrop is not going to get past the Mach wave attached to the front of a supersonic bullet.

That's right. The mach wave keeps the moisture off it but don't let a water drop hang off the barrel. I have and it can really de-tune the barrel
Andy.

mks
10-12-2015, 11:50 AM
A raindrop is not going to get past the Mach wave attached to the front of a supersonic bullet.

A common misconception. Air, water, whatever, flows through the Mach wave, which is just a transition in fluid properties, including pressure and density.

xs hedspace
10-12-2015, 12:15 PM
Two observations: I was scoring for a Marine sniper who went to a 1K match with his .308 issue rig for the practice, before there was an F class. He hit the spotter in the x ring about 5-6 times, went clean until the 20th shot, and it was a high 9. It started to rain halfway thru the relay, and my theory is that a drop landed in the muzzle, because he said that it felt like all the other good shots. BTW< he loaned me his USMC issue spotter scope, and I could see the holes in the spotter!
Other time a guy was shooting at a local ringer target at 100 yds in a downpour, and I could see a cloud of mist erupt on one shot about 60 yds out, and it still hit the ringer(but this was an AR firing at a 8" disc at 100 yds).

Wilbur
10-12-2015, 01:33 PM
As I wrote earlier, the probability of your bullet striking a rain drop is fairly slim. That statement is not of my own thoughts, but rather the result of some fairly exhaustive mathematics. If you shoot enough in the rain you're gonna hit a rain drop and the result is not likeable.

I'll say this and quit writing (yeah, really Wilbur), the probability of your bullet hitting a rain drop is fairly slim even in a moderate rain, but there is nothing physical involved - just the bullet being in the same place as a rain drop at the same time.

Chism G
10-12-2015, 01:57 PM
I've seen bullets hit rain drops. The impact vaporizes the rain drop. The impact on the target is usually no where near your group.

Some people call em "Rain Shots".



Glenn

Lawrence W.
10-12-2015, 02:34 PM
We have a shooter out here on the West Coast that is famous for hitting the very first drop of rain to fall! Just ask him if a "rain shot" is real.

Dick Grosbier
10-13-2015, 04:42 PM
I have always had some difficulty believing hitting a rain drop was likely to happen, but a few years back at the Pennsylvania state championship at York I became a believer. It was raining buckets and really coming down hard, one of the wettest shoots I ever attended in 30+ years. Several very good shooters had some terrible shots, 2 and 3 rings unexpectedly. I know of no other plausible explanation but "Rain Shots".
Dick

doghunter
10-14-2015, 05:52 AM
Thanks people.

Why I asked the question was that at a local club comp (.22RF, 100m) a few of the local 'hot shots' had unexplained flyers when a heavy shower came by. I commented that maybe a raindrop or two was impacted (.22 target ammo is sub-sonic btw, my Eley Tenex batch is 1062 fps).

I waited until the shower passed and managed to do ok. (1971 Anschutz M54).

As for the supersonic pressure wave, if anything deforms it, would not the resultant shock be passed back to the projectile and thus affect it?

Just curious so thought that I might ask the gurus.

* doghunter *

Wilbur
10-14-2015, 03:08 PM
If the rain drop doesn't hit the bullet, then how do you explain the "clean" bullet hole? All the others have a black ring and that one doesn't....just a hole in the paper far away from the group.

Dusty Stevens
10-14-2015, 06:31 PM
Its that damn wind.... I KNOW it is.

mks
10-15-2015, 09:08 AM
If the rain drop doesn't hit the bullet, then how do you explain the "clean" bullet hole? All the others have a black ring and that one doesn't....just a hole in the paper far away from the group.

Interesting that the errant hole is clean. I hadn't noticed this. Will have to look for it next time. Sure seems indicative of water on the bullet.

mks
10-15-2015, 09:18 AM
As for the supersonic pressure wave, if anything deforms it, would not the resultant shock be passed back to the projectile and thus affect it?
* doghunter *

Yes, that is logical, but the truth is that the Mach wave is not a magical brick wall that nothing can get through. If this were the case, then when you shoot a deer, the bullet couldn't penetrate, but only push the deer forward!

Fred J
10-15-2015, 09:19 AM
The pressure in front of the bullet pushed the rain drop into the target, and then the bullet followed it in.

mks
10-15-2015, 09:33 AM
As I wrote earlier, the probability of your bullet striking a rain drop is fairly slim. That statement is not of my own thoughts, but rather the result of some fairly exhaustive mathematics. If you shoot enough in the rain you're gonna hit a rain drop and the result is not likeable.

I'll say this and quit writing (yeah, really Wilbur), the probability of your bullet hitting a rain drop is fairly slim even in a moderate rain, but there is nothing physical involved - just the bullet being in the same place as a rain drop at the same time.

On the other hand, in a heavy rain (I did the calculations for a 1" per hour rain) chances are that every bullet strikes multiple raindrops. This is what I found interesting at the Buckcreek match several years ago, instead of an errant shot once in a while, every shot was pushed in the same direction. What I think this shows is that in a light rain, you may hit a drop once out of several shots, pushing that shot far from the group, but for a heavy rain, each bullet is struck so many times that the POI becomes consistent again, but much different from the POI without rain.

Wilbur
10-15-2015, 02:03 PM
I don't believe that's what happens, but each to his own...

brickeyee
10-15-2015, 04:06 PM
A common misconception. Air, water, whatever, flows through the Mach wave, which is just a transition in fluid properties, including pressure and density.

Even air does not flow over a Mach wave.

The Bernoulli equation fails since it assumes a standing pressure wave cannot exist.

classcat
10-15-2015, 05:52 PM
Skip the pistol part and go to the answer.

physics.stackexchange.com/.../how-does-a-hollow-point-...

brian roberts
10-15-2015, 06:57 PM
How can an "Air Wake" ever be in front of a supersonic bullet? The word "Wake" would denote a phenomenon/disturbance AFT of the bullet.

And, a "Mach Wave" would have to also be aft of a SUPER-sonic bullet, no?

And finally; Can it REALLY be "raining buckets"....and NOT be "coming down hard"??? ;)

It was an interesting read, I was just pointing out some amusing statements, when you think about them, 'course, some were pro'bly

made in jest anyway. :D

I have seen rain on a trap range when its easy to see the passage of shot through a decent rain.

I watched on a fairly calm day, a .17 travel downrange numerous times and generate a disturbance that tapered in an arrowhead-like manner

behind it, all the way out to 300yds; And I wondered if, at the area just aft of the bullet, that disturbance wouldn't alter the pattern of the rain if

a rain would intrude in this area during a storm.

Fascinating experiences, though, thanks for the info. :cool:

mks
10-15-2015, 07:36 PM
From Wikpedia: "Shock waves can travel through any medium, including solids, liquids, gasses, and plasmas."

https://en.wikipedia.org/wiki/Shock_wave

Mach waves are cone-shaped, and extend outward from the bullet in all directions, including to the ground. If air couldn't flow through the wave, then the bullet would have to push an increasing mass of air along with it as it traveled from muzzle to target. It would be lucky to go a few feet before it accumulated so much resistance that it fell to the ground.

The same sort of Mach wave extends from a supersonic aircraft at 10,000 feet all the way to the ground. If planes had to push everything in its path in front of their Mach wave, they couldn't fly.

When we hear a sonic boom, the Mach wave has passed through our bodies. It does not push us to the ground.

The cloud of water vapor that many of us have seen when a bullet strikes a raindrop is not pushed by the Mach wave past the target. The Mach wave passes through it.

Enough examples?:)

Cheers,
Keith

No need to bring Bernoulli into this.:)

Added:

Here is a better reference for the mathematically-inclined: https://en.wikipedia.org/wiki/RankineĖHugoniot_conditions

u2 in the first three equations (conservation of mass, momentum and energy) is the speed of air passing through the shock wave. u2 is not zero.

jackie schmidt
10-15-2015, 08:14 PM
At The Nationals in Phoenix several years ago, we had a sudden rain storm come in during my relay. The rain was not blowing under the firing line awning, it was just a steady downpour.

I had a shot go almost ONE INCH off from my group. This was at 100 yards.

This is not the first time I have had this happen.

classcat
10-15-2015, 08:38 PM
How do you post a photo ? I have some interesting pictures

coyotechet
10-15-2015, 09:26 PM
Very easy just go to the above third icon from the right (insert image) click on it and do as it says. First click on the below (reply to thread) icon.
Chet

classcat
10-16-2015, 12:15 AM
1694216942

The shock waves are different on H P Versus a pointed bullet, but in my opinion if it is raining hard enough and the distance is "100 Yards" both bullets will be deflected if the raindrop hits it. The weight of the bullet 68 grain should deflect more than a 168 grain

I M H O

Dick Grosbier
10-16-2015, 08:02 AM
Even air does not flow over a Mach wave.

The Bernoulli equation fails since it assumes a standing pressure wave cannot exist.

Waay over my head.

brickeyee
10-16-2015, 10:03 AM
From Wikpedia: "Shock waves can travel through any medium, including solids, liquids, gasses, and plasmas."

https://en.wikipedia.org/wiki/Shock_wave

Mach waves are cone-shaped, and extend outward from the bullet in all directions, including to the ground. If air couldn't flow through the wave, then the bullet would have to push an increasing mass of air along with it as it traveled from muzzle to target. It would be lucky to go a few feet before it accumulated so much resistance that it fell to the ground.

The same sort of Mach wave extends from a supersonic aircraft at 10,000 feet all the way to the ground. If planes had to push everything in its path in front of their Mach wave, they couldn't fly.

When we hear a sonic boom, the Mach wave has passed through our bodies. It does not push us to the ground.

The cloud of water vapor that many of us have seen when a bullet strikes a raindrop is not pushed by the Mach wave past the target. The Mach wave passes through it.

Enough examples?:)

Cheers,
Keith

No need to bring Bernoulli into this.:)

Added:

Here is a better reference for the mathematically-inclined: https://en.wikipedia.org/wiki/RankineĖHugoniot_conditions

u2 in the first three equations (conservation of mass, momentum and energy) is the speed of air passing through the shock wave. u2 is not zero.

If a Mach wave enters a jet engine inlet the engine is instantly choked off from the interruption of air flow.
The idea that the mach wave extends to infinity and represents an infinite load is grossly wrong in concept.
Over a limited area it is a standing pressure wave.
The pressure difference drops across the wave as you move away from the supersonic object.
Air flows AROUND the roughly cone shaped pressure wave, but not through the wave.

As velocity increases the Mach waves forms and attaches to the object.
It IS in front of the object at the front. How far depends on the density of the 'fuid' the object is moving in.
As velocity continues to increase the Mach angle (opening angle of the Mach wave that face backwards) becomes smaller and actual drag force declines.

Chuck Yeager was the first one with enough balls to go above Mach 1.
The other pilots tried to creep up.
Control force increased and buffeting occurred as the Mach waves attached.
The Mach waves had to be moved along with the control surface.

Even now we fly below Mach 1 or above Mach 1 (with some margin on each) but not AT Mach 1.

mks
10-16-2015, 01:31 PM
When flow is choked, it has reached a maximum that cannot be exceeded without changing the upstream conditions. The flow does not suddenly stop.

https://en.wikipedia.org/wiki/Choked_flow

The second equation gives the mass flow rate through the shock wave under choked conditions.

Again fluids, including air, flow through a shock wave, whether it is around a bullet or in a venturi.

brickeyee
10-16-2015, 07:56 PM
When flow is choked, it has reached a maximum that cannot be exceeded without changing the upstream conditions. The flow does not suddenly stop.

https://en.wikipedia.org/wiki/Choked_flow

The second equation gives the mass flow rate through the shock wave under choked conditions.

Again fluids, including air, flow through a shock wave, whether it is around a bullet or in a venturi.

Air does not flow over a shock wave.
That is the very definition of a shock wave in a compressible flow.

We sepent a lot of effort to keep the Mach wave out of the inlet of the SR71 engines a long time ago.
They mostly operated as bypassed ram jett.
The air flow choked instatly if the mach wave entered the inlet.
It made for spectacular pictures of flames from teh afgterburner.
they are very common pictures.

The computer (originally analog) immediately commanded full rudder to counteract the loss of thrust from an 'unstart' from the choked flow.
A pilot would never react fast enough to maintain control.

They complained about their heads striking the inside of the canopy the motion was so violent.

I have denstrated chocked flow for at least the past 20 years in my lab to undergrads.

I increase the pressure driving a gas though a small tube higher and higher.
The tube is instrumented with all sorts of mass flow, velocity, and pressure sensors (the purpose of the class is instrumentation).
As the flow speed increases the tiny perturbations the sensors create allow Mach waves to attach.
At the critical speed the pressure shows a step over a short distance, the mass flow drops to zero.
The tube is still open but the silence is deafening.
No more screaming gas.

If there is time we repeat it using a nozzle shaped to increase flow speed through a throat.

Part of the deonstration is to make sure students stay alert to how sensors can disrupt the very target of measurements.

mks
10-16-2015, 11:05 PM
I understand that it is difficult to reconsider a long-held belief, but please have a look at this short lesson on choked flow:

https://www.youtube.com/watch?v=DNURRIJz94k

At the 3:17 mark, the instructor shows a graph of mass flow rate as a function of back pressure. You see that mass flow rate is maximized when choking occurs at Mach = 1. Later he shows simulations of flow through the shock wave for different back pressures.

Here is a video in a supersonic wind tunnel of flow through a shock wave:

https://www.youtube.com/watch?v=BI7R8KiX8HU

Not only is there flow through a shock wave, flow is necessary for a shock wave to occur. The shock wave occurs where Mach = 1, i.e., where the speed of the air is equal to the speed of sound.

alinwa
10-16-2015, 11:56 PM
Holey Kowww.... this is why I quit arguing with teachers years ago....


the tiny perturbations the sensors create allow Mach waves to attach.
At the critical speed the pressure shows a step over a short distance, the mass flow drops to zero.
The tube is still open but the silence is deafening.
No more screaming gas.


OK, let's read it slowly....



the mass flow drops to zero


really?

mks
10-17-2015, 08:54 AM
If the mass flow dropped to zero, then there would be nothing to maintain the pressure and density differences across the shock wave, and the wave would disappear. You can't have a shock wave without flow.

Wilbur
10-17-2015, 01:20 PM
Not that I don't lose track a lot but.....are y'all saying that a bullet will or will not strike a rain drop?

If y'all have moved on to something different just ignore this post...please sirs.

Dusty Stevens
10-17-2015, 02:22 PM
A bullet may or may not hit a raindrop but i do know when its raining ive seen some good aggs destroyed in a rain relay. I mean 2" flyers. And it does it during the rain.

Chism G
10-17-2015, 04:02 PM
What's the difference between rain drops and insects ,of all dimensions. Not to mention flag tail material. Does rain drops possess some kind of magical protection from high velocity flying objects?




Glenn

mks
10-17-2015, 05:57 PM
Not that I don't lose track a lot but.....are y'all saying that a bullet will or will not strike a rain drop?

If y'all have moved on to something different just ignore this post...please sirs.

Wilbur,
I'm saying that a bullet CAN hit a rain drop, because air and water pass through the shock wave that surrounds the front of the bullet.:)

Keith

Wilbur
10-17-2015, 06:36 PM
Is there anybody that believes a bullet in flight can't contact a rain drop?

mwezell
10-17-2015, 07:28 PM
I think some will and some won't. Obvious. ..I know..but what I mean is that a direct hit will wet the bullet and a glancing blow may not. We've probably all seen a bird miss our windshield and many of us have bugshields...they don't all get blown off but greatly reduce the mess. I'm thinking that bullets and rain drops are the same way. Now, if that's true, does a drop that never physically touches the bullet but does the shock wave, affect bullet flight?

alinwa
10-17-2015, 09:04 PM
I do like guys who test stuff

https://youtu.be/UusiTSu1tSU

Wilbur
10-17-2015, 10:43 PM
I do like guys who test stuff

https://youtu.be/UusiTSu1tSU

Not the same as rain but shows what happens when bullets hit water...and that bullets will hit water. What the problem here is that a rain drop has got to be in the same place as the bullet at the same time. Given that bullets travel pretty fast it has to rain pretty hard for a bullet to be guaranteed to hit a drop. In fact, the probability is somewhat unbelievable. I surely wish I had kept those "figures" - but I didn't and the fellow that did the figuring is gone forever.

Chism G
10-18-2015, 09:56 AM
When shooting in the rain. Whatís the possibility of bullets hitting multiple rain drops on the way to the target? That possibility increasing with distance from muzzle to target and the rate of rain fall. Iím thinking that a bullet in flight to a target,when its raining, encounters a gauntlet of rain drops. Each succeeding impact ,with a rain drop ,affecting the flight of the bullet. Its amazing that the bullet impacts anywhere near where you aim. Sometimes,it doesn't.

Wind flags donít help much when youíre shooting in the rain. At least thatís been my experience.





Glenn

Pete Wass
10-18-2015, 10:14 AM
I do like guys who test stuff

https://youtu.be/UusiTSu1tSU

that rifle was capable of shooting inside a pie plate @ 300 in the first place?

Pete

Wilbur
10-18-2015, 12:13 PM
I think some will and some won't. Obvious. ..I know..but what I mean is that a direct hit will wet the bullet and a glancing blow may not. We've probably all seen a bird miss our windshield and many of us have bugshields...they don't all get blown off but greatly reduce the mess. I'm thinking that bullets and rain drops are the same way. Now, if that's true, does a drop that never physically touches the bullet but does the shock wave, affect bullet flight?

I don't know for sure but I don't think so. Just going with what I've seen on this one.

mks
10-18-2015, 01:24 PM
Whatís the possibility of bullets hitting multiple rain drops on the way to the target?
Glenn

I went back and looked at my estimate from 2009 and found that one of my assumptions was probably too large. A better scale for the diameter of the circle of bullet/raindrop strikes should be one bullet diameter and two raindrop diameters. With this new assumption, I get 2.83 strikes for a 30 cal bullet, and 2.14 strikes for a 6 mm bullet, over 200 yards in a 1" per hour rain.

Wilbur, your calculations may be more sophisticated than mine. Mine only took five lines.

At 1" per hour, the volume fraction of rain in the air is only one in a million, so if we were riding along on the bullet, we would see mostly air. But a real downpour, like the one at Buckcreek, could be much heavier.

mks
10-18-2015, 01:30 PM
... does a drop that never physically touches the bullet but does the shock wave, affect bullet flight?

Sure, it does. Think of an F-16 passing at supersonic speed an inch over the top of your truck. Both would feel the effect, even though they didn't touch.

mwezell
10-18-2015, 02:34 PM
Sure, it does. Think of an F-16 passing at supersonic speed an inch over the top of your truck. Both would feel the effect, even though they didn't touch.

I was thinking the same, Keith. That said, there must be some effect of pushing rain drops away, albeit, not necessarily a direct hit on one..or a wall of water such as coming off of a roof with no gutter.