Shooting in the rain

J

JasonYuke

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Got a question and looking for opinions about percision shooting in heavy rain!

Does or is the bullet effected by drag or and deflection happen.

I was shooting today and I found some intresting results? heavy vs light rain.
The wind was calm and I was only shoot 100m targets.
 
I believe the bullet is affected by the high percentage of humidity during rain. I don't think an actual rain drop could strike a bullet in flight as it creates a shock barrier around the bullet as it slices through the air.

I've experienced a drop upwards to 2 minutes @ 1000yds during heavy rains and then a return to normal elevations once the rain stopped suddenly.

Of course this is my opinion only and I have no data to back it up.
 
The air humidity is a big factor.

Moist,cool air will cause bullet drop as it is denser, while dry, hot air will cause bullet rise.You will notice in the spring/ summer that your POI will be higher then in the fall/winter

Also shooting over water (IE: Lake) will cause bullet drop because of the denser, moist air.

Hot Rodders/Drag Racers should know about this.......;)

SKBY.
 
TheIndifferent1 said:
We generally try not to race over water :D
Click to expand...


I actually meant in general, drag racers should know about air density/hot/cold air...............;)

Mission Raceway in Mission B.C. sits right beside the Fraser River and is known to have optimum racing conditions................ In fact, some of the best on the westcoast because of the idea atmospheric conditions........

SKBY.:D
 
Depends what your racing.
0136.jpg
 
High humidity, temperature, or altitude makes air less dense. Low humidity, temperature, or altitude results in denser air.

To illustrate how air density can effect us there is an interesting story concerning air density which occurred here some years ago. A small twin engine aircraft left Las Vegas at 2200' and a temperature of 82F and landed here at seal level at a temperature of -45C. Upon landing the tires on both sides of the plane went flat and there he was, stuck on the runway. His tires were nice and hard in the warm air, but the air in his tires became denser in the cold air at sea level, therefore took up less space, resulting in flats. For those knowledgeable about aircraft, it is not clear if the tires were originally inflated with nitrogen, but I doubt that they were.

A supersonic bullet passing through rain may-not be effected by the water drops it passes through due to it's shock wave, but when shooting in the rain our ammunition get wets, and wet ammo results in a different point of impact than dry ammunition. Water is not compressible, so it follows that a wet cartridge will result in higher pressure than a dry cartridge because the wet cartridge takes up more space in the chamber.
 
Decreased barometric pressure or high altitudes will result in a decrease in drag, and increased barometric pressure or low altitudes will result in a rise in drag.

Humidity also has an impact--the opposite of the one that most people expect.

Since water vapor has a density of 0.8 grams per liter, while dry air averages about 1.3 grams per liter, higher humidity actually decreases the air density, and therefore decreases the drag.
 
When air is given more heat, this results in added energy for the molecules. When air molecules have more energy, they move more rapidly and thus further apart, which results in fewer molecules occupying the same space; air pressure decreases. Similarly, as air temperature falls, the air pressure will increase.

Warm air near the surface will tend to rise. A mass of low pressure is an area of air that is rising. As is rises it expands and cools. Cooler air cannot hold as much moisture as warmer air, so as the air rises the water will condense and form clouds. This is why an area of low pressure will often be accompanied by clouds and rain.

Conversely, an area of high pressure is a section of air which is sinking. As the air sinks back toward the surface it warms, so is able to hold more moisture, and therefore will not need to condense and create clouds. This is why areas of high pressure are often accompanied by fair weather.

So, following this logic, high pressure brings more, dense air. The higher the pressure, the more drag the air will have on a bullet. I've attached a couple of images to show some numbers behind the logic.

Bullet drop, in inches, in standard barometric pressure (29.53 Hg)
bulletstandardor6.jpg


Bullet drop, in inches, in very high barometric pressure (35.0 Hg)
bullethighcs2.jpg
 
I believe the biggest effect, is the visual change you have with your sight picture. In heavy rain, it is appears that you are looking through a fog or blurry scope. This visual effect would be more than any physical effect on your flight path due to hitting a droplet or two.

Similar to the effect that bright light would have compared to low light or overcast.

Comments?
 
I found this yesterday at the range the first round was shot well, than the rain and winds came in and proved to me again how much effect on the bullet moisture had.

I was shooting 6mm BR and my groups went from avg .5 to .8s when it started to come down, same as the 6.5x284
 
My findings are the same as Canuckhunter, 1 1/2-2MOA elvation difference at 1000 yards. I think about half of it is denser air while the other half is lighting conditions.
 
I did some some shooting in, at times, heavy rain yesterday. I was shooting at 900 yards with my AR15. I didn't notice any difference in elevation settings though. When I was properly zero'd at 900y, I just kept plunking them in the bull or v-bull. My elevation was set at 25.5MOA up from a 100y zero, just as my ballistics calculator predicted. A side benefit of the wet weather was that there was little or no wind to contend with. Although my gear and I were soaked, I had an excellent shoot :dancingbanana:

So, does rain affect elevation setting? Maybe, but I couldn't realy tell :confused:
 
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