Rain affecting bullets

How about this? Put a tube of .500 diameter at .5 ches per hour, how often do you expect a bullet that travels for maybe two seconds to actually strike a drop?

Any time that the air density is extremely off average your velocity at long ranges. I can't pretend to know the actual effects. One fact is that if the air is much denser it will absorb more energy as it displaces the air.
 
Rain effects the shooter, not the bullet.

Same with snow.

Humidity does effect the bullet, but not the way more people think. Humidity actually helps the bullet, doesn't retard its flight.
 
For some reason I was just thinking that small of a bullet going that fast that any little thing could knock it off target.
 
I've just never had as good of luck with a 22-250 as I have with larger calibers. But it's also rare that I get good shooting conditions usually I am in the feed truck shooting at coyotes that are running the other way.
 
The thing to know about rain is that even when it's raining hard, there's very little of it actually in the air. An insanely fast rainfall is roughly 1"/minute of accumulated water - if it rained like that for 3 minutes, it would be a world record. Rain drops fall at about 40 mph, or 42,240 in/minute. That means during the hardest rain you'll never ever see the air is still 99.998% not water.

If you do get very unlucky and your bullet hits a raindrop square on, the bullet will be deflected. The desnsity of water is about 1/11th that of lead, so there's enough mass there to push the bullet around a bit.
 
There are two questions really.

With a moderate speed .308 match bullet, humidity going from 0% to 100% will equate to 1.5 to 2" difference in drop on the bullet at 1000 yards. In reality, it is minimal, but it does have an effect.

With a .22 caliber match bullet, the difference at 1000 yards is on the order of about 1 inch. Still not a huge affect.

As for actually hitting a rain drop, not going to happen while supersonic. The air at the tip of the bullet is heated and is a laminar wake. Displacement and sublimation of the rain drops occurs making actual contact with the bullet a mathematical improbability so high that it should not even be considered.

Testing has shown that air loaded with water (high humidity) has beneficial fluid dynamic properties to a bullet in flight. Shooting in 50% or higher RH will actually produce slightly smaller groups than perfectly dry air.

Wanted to add this. High humidity does very minimally reduce the MV at which the bullet leaves the bore, on the order of a few fps. But once we leave interior ballistics and go to exterior, the humidity is beneficial.
 
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Shotguns?

We shoot trap in the rain every now and again. Seems to have no effect at all on the shot. Has a great effect on the shooter tho.

The rain seems to do nothing and we have lots more, lots smaller projectiles and they are traveling far slower. Say 1100-1200 FPS vs. 3000 FPS
Now the wind.....that's a different story.
 
MarkCO said:
As for actually hitting a rain drop, not going to happen while supersonic. The air at the tip of the bullet is heated and is a laminar wake. Displacement and sublimation of the rain drops occurs making actual contact with the bullet a mathematical improbability so high that it should not even be considered.
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Technically true but it's sort of a distinction without a difference. Since the bullet is producing the pressure wake, anything that effects the wake will also effect the bullet. In other words, if the wake in front of the bullet "vaporizes" a water droplet, the energy source is the bullet.

The actual effect may be slightly different, if the bullet actually hits the water directly rather than being "shielded" by the wake but whatever energy gets transferred to the water can only have come from the bullet, meaning hitting a water drop will slow it down and/or deflect it by some amount.

I agree that the odds are astronomically small but the effect would be real if it happened.

There are videos that show a rain drop getting hit:
https://www.youtube.com/watch?v=HWSES47YkyM
 
Heated air, enthalpy of vaporization of water...If you choose to actually run the equations, you can see how the humidity, cooling, helps the bullet in flight, not hinder it. Yes the energy comes from the bullet, but it is already wasted in heating so vaporization of rain drops has no effect (unless you have a REALLY big rain drop).

I did the calculations in grad school and no, I am not doing them on the internet. :D
 
The fact that you can see the target through the rainstorm is an indication that light rays made it to your eyes without hitting a single raindrop.
 
Brian Pfleuger said:
Lots of analysis
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Your calculation is not correct, you do not have the proper volumes involved.

The .308 bullet in question is .308 inches wide (diameter) so we will consider a plane that is .308 inches by 36,000 inches (1,000 yards). Any point on this plane will be struck by the bullet as it travels, to be completely accurate, we'd have to consider the full circumference of the bullet, but that's too complicated and would make it even more likely to hit a drop anyway.

Our plane has 36,000*.308=11,088 square inches of area. We will assume a rainfall rate of 1 inch per hour (quite heavy) and that gives us a total volume of 11,088 cubic inches of water on that plane per hour, or 11,088/3,600=3.08 cubic inches per second.

We will assume an average raindrop size of 3mm in diameter, which is probably a reasonable assumption since drops generally split when they exceed 4mm. That is 0.118 inches in diameter, or 0.059 in radius, which gives us a volume of 0.059^3(4/3)*3.141=0.00086 cubic inches per drop.

This means that each second, 3.08/0.00086=3,581 drops will pass through that plane. So, over the bullet's 2 second flight time, 7,162 raindrops will cross its flight path.

The math to calculate the probability of how many drops it will actually hit is quite a bit more complicated, but just from the number of drops, you can reasonably assume that it's going to hit quite a few of them.

Now, multiply that by 5 for the 5 inches per hour that the first analysis did (which is a hurricane).
 
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I have now reached the point of saturation.too much rain and not enough coffee.

I would like to suggest that one of the sharpshooters here lay out a jug of trickling water, and put a dozen rounds through that stream with a 17 harm. Use backer boArds to record effects.
 
I think folks are saying that the next time I shoot a 10" group at 100 yards I can't blame that rain cloud over the hill a mile behind me. Darn it, and it sounded like a good excuse!

Jim
 
I think folks are saying that the next time I shoot a 10" group at 100 yards I can't blame that rain cloud over the hill a mile behind me. Darn it, and it sounded like a good excuse!
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Nope, but you can rest assured that if you talk about a 0.103" group here, there will be someone piping up with, "But that was just because of the 98% humidity! Do it again on a dry day!"
;)
 
mapsjanhere said:
While rain doesn't do anything on shooting a small bullet short distances it's interesting in what it does to a high speed interceptor missile fired in a storm. At 6000 ft/s it looks like the nose is getting sandblasted, losing fractions of an inch in material.
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I have heard that flying through a rainstorm can really chew up the tips of a wood propeller on an airplane.
 
The math to calculate the probability of how many drops it will actually hit is quite a bit more complicated, but just from the number of drops, you can reasonably assume that it's going to hit quite a few of them.
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I've followed up to this point, and the calc's are simple and seem to be logical and correct to me...far as dispersion of the raindrops, and probability...

The rest is over my head. My son's an aerospace engineering major that does calculus for "fun"...maybe I'll run this by him :D
 
I was at the range one day when there was a very heavy rain storm. At 100 yards I could not see any difference in the group fired by my 30-06.

On the other hand while shooting a crosman model 1377 pellet pistol at 20 yards my group went from around one inch to over 5" with a moderate rain. As soon as the rain quit the groups went back to normal size.

So the bullet speed with a cushion of air ahead of it may be the difference. I'll leave all the math up to you brainiacs.;)

It always makes me smile when I read about guys wanting a stainless/synthetic rifle so they can hunt in the rain. Not me, if its raining I stay in camp and play cards. Contrary to popular opinion I am made out of suger and I will melt.:D
 
ratshooter, :D


As for rain impacting shooting...
This was at 100 yards, shooting PPU 5.56x45mm 69 gr "Match" ammo, in about 1" per hour rain with a 15 mph tailwind, after 45-50 minutes of rainfall, and the targets were nearly dripping off the backers:
(I shared this photo for other reasons a few months ago)

attachment.php


Five rounds stacked up for 0.347".
Number six more than doubled it, for 0.703".

Number six was ALL me. The rain had nothing to do with it.
...And still one of the best groups ever fired by that rifle.

(Point of aim was the blue globe on the right side. That load impacts ~3/4" left, for some reason.)
 
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