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# Shooting in the Rain?

#15
11-04-2005, 12:42 PM
 Bronze Member Join Date: Jul 2005 Posts: 32
Re: Shooting in the Rain?

lb1000br,

I have been thinking about that too, and I agree. I think the shock front is acting as a bug shield and deflecting most glancing blows. The drop would have to either be a direct hit or be large enough to penetrate or deflect the shock wave sufficiently to apply a force on the bullet. Or maybe the drop would vaporize as the wave passes through it and you have an angry little puff of expanding water vapor along side the jacket. Those are just ideas -- I don't know enough about gas dynamics even to make an educated guess.

If you say water is 62.4 lbs per cubic foot, 0.008 grams would imply a drop diamater of 0.038" or a little less than 1 mm. Sounds reasonable.

If all momentum is transferred to the bullet there would be two possible effects: lateral velocity and yawing/destabilization. I'll not touch the latter as it is way out of my expertise, but lateral velocity should be vanishingly small with a single hit, something like a millionth of a meter per second. If you do energy transfer methods with phase change and the like, it should come out roughly the same order of magnitude.

So a single average drop is not capable of deflecting a bullet significantly, or at least that's the way it looks to me.

If you take the same 0.038" diameter drop and figure an inch of rain per hour, that is 1.2 such drops per square inch per second. If you say that the bullet's effective cross section (due to shock wave shielding) is 0.1", then the "impact circle" is 0.138" diameter. 1.2 of those circles has an area of 0.015 square inches. So the probability of a hit is 0.015 square inches per square inch or 1.5% -- in 1" of rain per hour.

If you shoot 200 bullets in that rain, 3 of them will hit a single drop on their way to a distant target. The effect of those hits is probably not measurable.

So that's my scrutiny, for what it's worth.

Scott
#16
11-04-2005, 02:16 PM
 Silver Member Join Date: Jul 2004 Location: Upland, CA Posts: 423
Re: Shooting in the Rain?

This is all fine, but if barometric pressure can cause a bullet to strike high....and it does, when I travel from coastal California to Colorado, and I have to rezero, then I don't really see why the denser air from 100% humidity (dewpoint) would not affect the performance of a bullet as it does to aircraft?

I have done a little shooting in the rain and managed to hit what I was aiming at but accurate work under field conditions makes the shot a little less of a sure thing, all due to the visibility factor, if nothing else.

And, I'd like to know if these 1000 yard matches, where shooting in the rain doesn't make any difference; are covered and protect the shooter and his scope? Probably yes? The times I have shot in the rain, (me, rifle and target) contrary to what I am reading here, I think I was at a disadvantage. Should the above calculations convince me that it was all in my head, or what? The consensus seems to be: "no problem".

Good hunting. LB
#17
11-04-2005, 02:27 PM
 Platinum Member Join Date: Jul 2003 Location: Central PA Posts: 1,307
Re: Shooting in the Rain?

Last time i shot in the rain was covered - williamsport

but the rain was coming in at such an angle, aided by the wind, that it got the whole rifle and scope lens wet [img]/ubbthreads/images/graemlins/laugh.gif[/img]

so i was standing in front of it shielding with my body till we were ready to shoot [img]/ubbthreads/images/graemlins/laugh.gif[/img]

my group that day had a bit over 5" of vertical, but centered in the 10-ring

Diane Hoover won her relay with 13.9" and i was 3rd with 15.6...all windage from the center to the right...diane was the only one to pick it up!

This was match 10 at williamsport

There were some HUGE groups fired that day!

JB
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#18
11-04-2005, 05:52 PM
 Platinum Member Join Date: Jun 2001 Location: Potomac River Posts: 5,088
Re: Shooting in the Rain?

Physics is physics- an impapct on the shock wave is an impact on the bullet --by compressing the air that is already compressed you affect the bullet. This is why depth charges destroy submarines, except in reverse.
Think about it this way. When a bullet hits a deer, does the shock wave protect the bullet from being deformed ? No. The lead tip mushrooms out becuase the mass of the deer impacting on the shock wave pushes the shock wave out of they way. In tissue, a second shock wave arises in the new semi-fluid medium.

Vaporizing a drop of water requires how many kcals of enrergy? Check a CRC handbook. Where does that energy come from? Transferring bullet kinetic enregy to heat of vaporization is lost energy which can be computed back to momentum loss which is my point except you have now complicated a simple analysis and you still get the same answer.

I could easily be wrong about some of this but two points are valid. My calculations indicate the same thing as you say - in a light rain there is no noticeable effect on bullet drop even at 1000yds.

Secondly, the shock wave does not do anything significant regarding the impact except much like in nuclear physics it increases the target radius for the collision. The significant fact is that a raindrop does not weigh much and is traveling slow so the impact is trivial.
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#19
11-04-2005, 06:40 PM
 Platinum Member Join Date: Jun 2001 Location: Potomac River Posts: 5,088
Re: Shooting in the Rain?

Leonard

I think that people like JB who shoot rain or shine at known distances with the same gun would pretty much notice it if there was much of a noticeable affect from rain. For people like you and me, we are mostly just cold and miserable with a wet scope and wet glasses and stiff muscles. The only thing worse than hunting in the rain is killing something in the rain.

There is one thing that has come up that I did not know about hunting in the rain until somebody got to talking about oil in the chamber and bolt thrust. Water is a very good lubricant like a fine oil. Water on a cartridge case once chambered would be like shooting with an oily chamber. Lots of bolt thrust and high pressures and who knows where the bullet would go.

P.S. I have never killed a coyote but I enjoy visting your forum because y'all have good jokes. I especially enjoyed the one about how many coyote hunters are divorced [img]/ubbthreads/images/graemlins/grin.gif[/img]
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#20
11-04-2005, 10:13 PM
 Bronze Member Join Date: Jul 2005 Posts: 32
Re: Shooting in the Rain?

[ QUOTE ]
Physics is physics- . . .

[/ QUOTE ]

Sorry, I was trying to agree with what you posted earlier. I didn't mean to sound like it was my idea or that I was contesting. You said "scrutinize" so. . .

Anyway, a main aspect to me is the low probability of actually hitting a drop. With the 1000-yard target and 1"/hr heavy rain you only have something on the order of a 1.5% chance of hitting even one drop. In a more realistic rain at a range that is, well, more my speed [img]/ubbthreads/images/graemlins/smile.gif[/img] , you have more like 0.25% chance -- statistically you'd have to shoot 400 shots at 500 or so yards to have one droplet impact. And half of those would be downrange where it matters least.

At the risk of seeming like an ass for saying this, the more I think about this problem, the less I think shooting experience has to do with the effects of an impact. If shooting exerience shows that rain is not a problem ballistically, what does that mean? It might mean only that the bullet is not likely to impact a drop. That doesn't tell you anything about what happens when it does hit a drop.

For practical purposes it doesn't matter beyond that. You shoot without correction in the rain and that's the end of it, because you don't have to care what happens when a collision occurs.

I'm still curious though, and I think I made a mistake above by not accounting for the water's final velocity as it is bounced off the bullet. I keep getting large deflections on the order of a few meters per second sideways. And the energy from vaporization is surprizingly large -- 44 kJ/mol, or 20 J (14 ft-lbs) for that 0.008 gram drop. Those effects seem excessive to me.

Scott
#21
11-05-2005, 12:50 AM
 Silver Member Join Date: Jul 2004 Location: Upland, CA Posts: 423
Re: Shooting in the Rain?

Thanks for the compliment, Bob. Appreciate it.

But, instead of trying to do the calculations and prove this question on paper, I can only think of one way to convince me that the rain has no effect.

As in Hollywood where they make fake rain, I would like to see a shooter zeroed on a target at a given range, then turn on the showers and see what happens. If he is still on target, my intuition is out of whack. But I have a hard time thinking that the bullet is going to plow through all those rain drops like they are nonexistant. As in no effect. Seems like, at some point, there has to be an effect. Maybe if you could rig sky screens right before the target, and see if the rain slows the bullet down? As I mentioned above, the air is denser with 100% humidity, so why is that different than less dense air at high elevations?

Good hunting. LB

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