Ballistic with rain?

[Javier]

I know about the humidity, but what happen with the rain.
Last weekend I was shooting at 300 meters away and for my 308w (Steyr SSG 08) this means 6.5 Moa up from 0 (100meters). But I used 7.5 MOA and not 6.5 when the rain starts.

What happen in ballistic when is raining?

(About Ambient air density:

Air temperature, pressure, and humidity variations make up the ambient air density. Humidity has a counter intuitive impact. Since water vapor has a density of 0.8 grams per litre, while dry air averages about 1.225 grams per litre, higher humidity actually decreases the air density, and therefore decreases the drag.)

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[wwbrown]

Light rain can act as the ultimate wind indicator it seems some of my best scores have been in the rain. The reason for the scores might be that in this area a light rain is often times paired with a complete laydown of the wind.

I shoot through the rain, I always have foul weather gear in the truck, I carefully dry and clean my guns when I get home. Guns are made to shoot and fully cleaned and oiled after getting wet, and yes I shoot custom guns.

 

[brian427cobra]

Re: Ballistic with rain?

I use Density Altitude, once your ballistic program is trued, it will be spot on and trust worthy out to 1 Mile.

You need to shoot often thru a chronograph.
You need a accurate device to measure atmospheric conditions
You need a logbook

You need to shoot, measure, document, or basically the first three recommendations, and take every shot like its your last.

Density Altitude doesn't care if its sunny or raining or hot or cold, Brand Cole is the inventor/discoverer of using DA in shooting, he also makes Prometheus Scales.

 

[Javier]

So rain has no effect in ballistic, is Air temperature, pressure, and humidity variations make up the ambient air density. Humidity has a counter intuitive impact. Since water vapor has a density of 0.8 grams per litre, while dry air averages about 1.225 grams per litre, higher humidity actually decreases the air density, and therefore decreases the drag.... but rain dosnt matter.

Thans for your answares.


http://en.wikipedia.org/wiki/External_ballistics

 

[Cold Bore]

Light rain can act as the ultimate wind indicator... The reason for the scores might be that in this area a light rain is often times paired with a complete laydown of the wind.

Agreed.

Even if the wind doesn't lay down completely, it is often light and steady during drizzly weather.

And even for guys that can't read wind or mirage on sunny days, you REALLY can't go wrong by watching the rain drops on a drizzly day.

If you can shoot from under cover, during a light drizzle, you might be surprised at how much you like it. 8)

 

[butchlambert]

I have shot very well in a steady rain. Just make sure you don't get any moisture in your barrel.

 

[jhord]

"Lights up, sights up?"

 

[Cakes]

++ to Wade's & others comments about rain usually "laying" the wind down for a nice group. I too have shot some of my best groups at 200 under our covered range in a light mist or fog. My .284 seems to throw out these mid teen groups any time its misty out. Can't seem to reproduce those groups even on a calm overcast but "dry" day...just don't know?? I would've guessed the moisture in the air would have a detrimental effect on the ballistics of a bullet, but apparently not at 200 yards with a bullet in the 162-180 weight range. Eric in DL

 

[pdhntr]

... But I used 7.5 MOA and not 6.5 when the rain starts.

What happen in ballistic when is raining?

I am just guessing, but there was probably a slight downward movement of the air as the rain was falling. Cool air sinks, warm air rises.

If the "parcel" of air with the rain was a little cooler than the surrounding air, it would be sinking. Thus causing you to have to dial up just a little to counteract it.

This is not to say that in every shower this will happen. There would have to be a temperature gradient for one parcel of air to sink while another is rising.

Jim

 

[ridgeway]

Its pretty cool to see the vapor trail going downrange, especially at 1K.

 

[D-mon]

Question: does the bullet touch the droplets of rain? Or does the shock wave created by the supersonic speed blows the droplets out of the way of the bullets?
And if the bullet does indeed touch the droplets, does that slow it down more which would explain the difference of impact at 300yrds experienced on one of the above post?

Nic

 

[butchlambert]

A few years ago I had the opportunity to watch high speed photography of a pretty good down pour. Slowing down the video makes it appear a bullet would be lucky to hit a raindrop. I personally think a bullet doesn't actually touch the bullet.
Maybe Bryan Litz could tell us. I just sent him an email.

 

[butchlambert]

Just received this email from Mr. Litz

Butch,

I’ve had the distinct pleasure of shooting in a lot of rain myself. As long as the sights and ammo stays dry, I’ve seen no ill effects either.

If you can see a target at long range thru the rain, the density of the raindrops has to be below a certain level; like 1 raindrop per cubic foot for example. It’s possible that at this density level, the statistical odds of a bullet encountering a raindrop are low. It’s also possible that encountering a raindrop doesn’t deflect the bullet. Regardless of the cause, we’ve both observed the effect, or lack of effect.

If you can keep sights and ammo dry, the rain can actually help you shoot better; it’s an excellent wind indicator.

-Bryan

 

[Javier]

Thans for all your answare, really, thank you very much.