How much does rain or snow affect ballistics?

[taliv]

lot of bogus info in this thread


i'd encourage you to stop and think for a minute about how much rain is actually in the air. a moderately heavy rain would be 1" of rain per hour. terminal velocity on a raindrop is going to be between 10-20 mph depending on size. converting units, it takes 1 / 352 of a second to travel one inch. so if you took every drop that crosses your bullet's path for the entire hour, it would pass in a tiny fraction of a second. there are 3600 seconds in an hour. so you can see the odds of your bullet actually impacting a rain drop in a heavy downpour are actually extremely small.

however, if it DOES impact a drop, as was stated above, it will affect the bullet. there are a few youtube videos out there of experiments where they hit a drop on purpose. I shoot in rain and snow every chance i get, and matches are often in inclement weather. I can't ever recall having my trajectory affected by rain or snow. (though watching your trace in both is really cool)

regarding the shockwave affect.... i'll offer this for your reading pleasure http://naca.central.cranfield.ac.uk/reports/arc/cp/0827.pdf


practical effects of shooting in the rain are:

rain makes it easier to estimate the wind
harder to see through ocular lens (objective isn't affected quite as much)
causes a lot of popped primers due to overpressure from wet ammo
harder to write on wet databooks and PDAs (though i have lots of write in the rain notebooks)

you can pretty much ignore the changes to ballistics other than associated humidity/DA changes

 

[CLP]

Live fire testing we did at the sniper school to confirm other tests with multiple weapons proved no effect.

No appreciable affect at the distance and conditions in which you shot...
And you lacked a control group of identical shots fired, with the exact same environmental conditions minus the rain, and we don't know how many shots were fired and if that number is enough to be statistically significant (n=?)
Anecdotal information is weak.

 

[CLP]

...the odds of your bullet actually impacting a rain drop in a heavy downpour are actually extremely small.

The odds of a single bullet...
I'm not taking about a bullet being fired at a deer. Or 30 bullets being fired in an hour.
I want to know, very simply, "Can rain affect the accuracy of bullets?"

The actual effect of rain on bullet accuracy can't be practically demonstrated but I'm arguing that it can be demonstrated under experimental conditions.
Enough bullets have to be fired for a comparison with a control group to be statistically significant.
You can't control the variables unless under artificial conditions (rain isn't constant- its intensity fluctuates, plus it would be so much easier to eliminate wind as a variable).
And I'd also argue that people don't shoot as much in the rain vs ideal conditions.
The rate of firing itself would be a factor in accuracy due to barrel heating.
And those are just a couple of the innumerable variables that would have to be considered and controlled.
And when I say controlled, I mean that we eliminate these variables to soundly answer the question- "Can rain affect the accuracy of bullets?"

So- I'm saying that under controlled conditions rain affects the accuracy of bullets.
Technically, I'm hypothesizing this. For the sake of argument, let's envision an indoor range where all the countless variables could be controlled such that our "rain group" and our control group were precisely identical save for the presence of rain (at a consistent downpouring) in the former group. This is the best environment because we can eliminate wind- and even control for other environmental factors as well (pressure, temp, humidity, etc).
The "rain lane" has a magical rain machine that mimics a heavy downpour in a consistent manner. I'm arguing that given enough shots fired, the "rain lane" would display worse accuracy- again, controlling for all other factors. At least, enough difference in accuracy as to be measurable.

It's only in this theoretical scenario that I'm arguing that one could demonstrate an effect on accuracy.

Practically? I find it very reasonable that one doesn't see any effect at all- and there's no shortage of folks who shoot in the rain and will attest to this. Argue all you want that under practical shooting conditions rain has no measurable effect on bullet accuracy and I would agree with you. But given enough shots, then I would argue rain does have an effect on bullet accuracy and I believe it can be demonstrated.
However, I do prefer to stay inside where it's dry when it's raining and go online and spend hours putting forth arguments over trivial matters.

 

[someguy2800]

Update:
This is a popular Werner Mehl / Kurzzeit video. Okay, the whole entire video is just pretty danged cool. But the video I was referring to starts at 1:59.

That is not a glob of liquid, it's a lead projectile fired from another gun intersecting with the pistol bullet.

 

[taliv]

The actual effect of rain on bullet accuracy can't be practically demonstrated.

sure it can. it would be easy enough to set up an experiment that causes a single bullet and a drop of water to collide, and then track on high speed film the change in the energy and path of the bullet.

 

[mcb]

I did this back of the envelop calculation some time ago. It makes a lot of assumptions but should give you a rough idea of how likely a bullet is to encounter a rain drop. Also notice how very little mass a rain drop has so even if there is a collision the rain drop cannot impart very much momentum to the bullet. Again just quick and dirty but I think it helps gives some perspective on the topic.

Assumed rain drop diameter: 2 mm
According to wiki rain drop vary in size from .1 to 9mm all though they frequently break up when over 5mm
volume: 4.18879 mm^2
Assumed spherical rain drop which is fairly accurate up to about 2mm
Mass of 2mm drop: 0.041888 g
0.646431 grains

NASA defines: Light Rain 2 - 4 mm/hr, Moderate 5 - 9 mm/hr, Heavy 10 - 40 mm/hr, Violent more than 50 mm/hr
Assume Heavy Rain 40 mm/hr
0.011111 mm/sec

Terminal velocity of falling rain drop 10 m/sec
10000 mm/sec

Fraction of a unit volume of space that is rain 1.11E-06
Calculated by dividing the rain fall accumulation per second by the terminal velocity

Bullet Diamter 0.338 in
8.5852 mm

Collision Area 124.3971 mm^2
Area is calculated based on the bullet diameter plus two times assumed rain drop diameter to include all possible collisions from direct impact to bearly kissing edge hits.

Range to target 1000 yards
914400 mm

Collision Volume 1.14E+08 mm^3
Simply the collision Area times the distance traveled to target

Number of rain drops possible withing that collision volume: 30.17277
Simply the collision volume time the fraction of the volume that is rain divided by the volume of a rain drop.
Remember these 30 rain drops would be fairly evenly distributed across the collision area and thus could be anything from a head on collision to a very tangential collision.

ETA: In short, IMHO, rain has very little if any measurable effect on the exterior ballistics of a bullet.

 

[Jack B.]

 

[CLP]

sure it can. it would be easy enough to set up an experiment that causes a single bullet and a drop of water to collide, and then track on high speed film the change in the energy and path of the bullet.

In controlled conditions- not in real-life conditions.

 

[Skylerbone]

Argue all you want that under practical shooting conditions rain has no measurable effect on bullet accuracy and I would agree with you.

And if we can disregard all of the side noise to get back to the threads original question, this is where we stand in answering.

 

[taliv]

Mcb if you're saying that an avg bullet is going to hit 30 rain drops on the way to a 1000 yard target, your math is way off. If there were 30 rain drops in the path it wouldn't even be possible to see the target.
Did you take into account how long the bullet would be in the impact area? I didn't see it. Seems relevant.

Also rain drops are never spherical though I don't think that matters.

And while a drop of rain may weigh a lot less than a billet a deflection of .017 degrees would generally be considered an unacceptable outcome to most target shooters

 

[FL-NC]

No appreciable affect at the distance and conditions in which you shot...
And you lacked a control group of identical shots fired, with the exact same environmental conditions minus the rain, and we don't know how many shots were fired and if that number is enough to be statistically significant (n=?)
Anecdotal information is weak.

All information is anecdotal, unless you conduct the experiment yourself. Which we did, and I encourage you to do.

 

[Klint Beastwood]

The bullet doesn’t lie. Inside ranges most of you shoot at there is a little measurable change. For shots well beyond 1000y that .003ish mils will add up to something measurable. So I suppose the answer should be, it depends.

 

[CLP]

All information is anecdotal, unless you conduct the experiment yourself. Which we did, and I encourage you to do.

But that wasn't an experiment using any valid methodology- so, interesting perhaps but it wasn't much in the way of offering any insight other than to say little to no observable change in accuracy was noted under those conditions under which you shot. There's likely a miscommunication in wording as well. My use of "experiment" has a very specific meaning vs. "I experimented with Pasta Roni last night by adding an extra pat of butter- which makes it better". Same thing between whitecoats using the word "theory" vs. when I say, "I have a theory about why Spam tastes so good" or something to that effect.
The problem with calling what you did an experiment involves conditions/factors which you cannot define because they're kind of indefinable real-world dynamic phenomena which prevents you from being able to control for them and the lack of a control group against which to compare the "experimental" group.

That being said, this thread's departure from the OP's question is totally my fault since it's obvious he/she intended the answer to reflect a real-world situation and I took it in a theoretical direction. I do think a rain vs rain-free comparison of bullet accuracy which is statistically significant and measurable is doable in an indoor range allowing for control of other influencing factors- and I think it'd make for interesting reading as well.

 

[d2wing]

Living in Minnesota I get to shoot in all kinds of conditions including heavy rain and snow. For ranges under 400 yards there is no noticeable effect. The biggest concern is keeping you sights dry and not fogging anything up.

 

[30Cal]

I shot one of my tightest 300yd rapidfire strings in a downpour off my submerged shooting mat. I could barely make out the bullseye and decided simply to stick the front sight in the middle of the target frame.

 

[FN in MT]

Good Lord! There are a LOT of You here that truly do like to ARGUE.

 

[JeffG]

Good Lord! There are a LOT of You here that truly do like to ARGUE.

Predictable thread devolution.

 

[taliv]

sorry, I'm missing the thread devolution. what are you talking about?

 

[1KPerDay]

More like escalation. I have my answer but it's fun to hear more from the ballisticians

 

[JeffG]

sorry, I'm missing the thread devolution. what are you talking about?

A lot of threads head into argument for seemingly no other purpose.

 

[CLP]

A lot of threads head into argument for seemingly no other purpose.

Sorry if my posts were interpreted as that way. That wasn't my intention.

 

[jmorris]

One such expert recently told me that I should avoid hitting raindrops with bullets when hunting.

Did he suggest the best way to shoot around them?

I have shot rifles for decades but I have never done any testing in this area. I have shot rifles sighted in under sunny conditions, in the rain and hit what I needed to and vice versa.

I have killed lots of animals in rain, sleet, snow and fog, I could tell if the bullets were wet or any effect they had in reguards to effectiveness vs ones during dry conditions. About the same as effects of daylight vs darkness, for hunting.

Lanny Bassham wrote in “With Winning In Mind” about shooting in the snow but his book is about mental management not external ballistics.

 

[1KPerDay]

well I'm back with numb fingers and toes. 32 degrees, not much snow and wind to start but then the front moved in and it got pretty chilly. Had a great time and my brother-in-law and his boy also. Got my dad's old .270 sighted in pretty well. It's built on a 1903 Springfield action and isn't bedded or free-floated or anything so I was happy with my 1-inch 3 shot group at 100 yards with the cheaper Federal factory SP hunting ammo before the group started to open up as the barrel heated. We also sighted in and shot his FN suppressed .308 bolt gun (looked like a winchester model 70 action to me) and only got to shoot at 200 yards before the wind and snow became unbearable... but he had never shot at any distance before and had a great time. I was able to hit a 9-inch plate every time with that one, prone from bags. We also shot my M1A and M1 Garand, which he loved. He hit 5 in a row on a steel 2/3rds torso open sights at 200 yards which had him really excited.

We were shooting through dead trees and brush for some of the positions and they DEFINITELY had an effect when struck, but the snow I'm not sure it had any, other than freezing us out. I'll post some pics later if I remember. The experience did do one thing for me which was make me want to get a dedicated longer-range bolt gun and optics and LEARN HOW to actually shoot it properly from field positions.

I was hitting the torso offhand with my M1A and Garand pretty regularly, like I do in 3-gun, but prone I could barely hit it. typical for me. I guess I shoot patterns more than groups with those rifles. LOL

 

[cp1969]

Are you sure those "droplets" at 1:59 are liquid? For one thing, they appear to be traveling as fast or faster than the bullets.

edit: Sorry, I overlooked post #29.

 

[1KPerDay]

I'm the fat guy in the orange hat. The group is on an 8-inch target and the first three shots are at about 4 o'clock. Shots four and five were further out at 3 and 5 o'clock.