Effect of rain on accuracy? (At 100 yards)
- Thread starter Danattherock
- Start date
TikkaSporter said:
Probably not vaporized raindrops as much as just condensed humidity. When raining the air is usually at 100% humidity and the turbulence can cause water molecules in the air to coalesce into more raindrops forming a contrail of sorts.
Happens in my part of the country all the time.
4xforfun
Gold $$ Contributor
Some food for thought.
"bullet never hits the rain drop because the drop actually hits the shock wave".
The shock wave of a supersonic bullet is BEHIND the nose of the bullet.
"ask an F-15 pilot if the raindrop ever hit their windshield at MACH 2". First, how many F-15 drivers have actually seen Mach 2? An f-15 CAN reach MACH 2 at altitude (where there are no rain drops)....or in a dive. NOBODY dives into rain at mach 2 unless he is in MUCHO TROUBLE in combat, and if it happened, he wouldn't remember if there was a rain drop problem. ;D
No, I like the theory that there just are not enough drops to hit on the way to the target. But, I just can't imagin that with all of the shots fired downrange in the rain that NONE of them ever hit a rain drop!! I just can't get there, either.
I will put this question in the same catigory as "are we alone in the universe".
"bullet never hits the rain drop because the drop actually hits the shock wave".
The shock wave of a supersonic bullet is BEHIND the nose of the bullet.
"ask an F-15 pilot if the raindrop ever hit their windshield at MACH 2". First, how many F-15 drivers have actually seen Mach 2? An f-15 CAN reach MACH 2 at altitude (where there are no rain drops)....or in a dive. NOBODY dives into rain at mach 2 unless he is in MUCHO TROUBLE in combat, and if it happened, he wouldn't remember if there was a rain drop problem. ;D
No, I like the theory that there just are not enough drops to hit on the way to the target. But, I just can't imagin that with all of the shots fired downrange in the rain that NONE of them ever hit a rain drop!! I just can't get there, either.
I will put this question in the same catigory as "are we alone in the universe".
I'm thinking a bowling ball going 100 mph wouldn't have its path affected by smashing the occasional egg along the way. I can't wrap my head around the two fore mentioned theories, so there it is, bowling balls and eggs by Dan. Look for it in the upcoming Physics Today. Heading to range shortly. If the trip down the barrel doesn't wear off the Rain-X I should be able to shoot a few good groups. Hah. Thanks for the thought provoking comments.
Dan
Dan
CatShooter
4xforfun said:
I think two things - first, those of us that shoot in the rain (my very bestest groups have been shsot in a drizzle), do not shoot in a roaring downpour, where the chances of a hit would be higher... we shoot in light rain/drizzle where the chances are all but nil.
Also, it is probably, "with all of the shots fired downrange in the rain that NONE of them ever hit a rain drop!!"... that you would net see it if one did.
There is not enough water to make a splash, and if it affected the bullet, it would be chalked up to a "Flier" (I didn't do my part all day, but it was cuz of the rain).
Why guess when you can do the math?
The basic information on rain can be found here: http://www.shorstmeyer.com/wxfaqs/float/rdtable.html
If we assume a light rain (2.5mm/hr, 2mm diameter raindrops traveling at 6.5m/sec = 23.4e6mm/hr), the volume of a single raindrop is 4.1mm^3, and the number of raindrops in a column of air 1mm^2 at the base * 1hr tall can be calculated as 2.5mm/hr / 4.1mm^3 = 0.61. The density of raindrops in the air is, therefore, 0.61/23.4e6 = 2.6e-8 raindrops/mm^3. The volume of a 6mm bullet's path over 100 yards (= 91m = 91000mm) is pi*3mm^2*91000 = 2.6e6mm^3. On average, then, there are 2.6e-8 * 2.6e6 = 0.07 raindrops in the bullet's path. Put another way, there will be a raindrop (or at least part of a raindrop) in the bullet's path in 1 out of every 14 shots or so.
But the bullet doesn't occupy its whole path at the same time. A bullet 25mm long occupies 25/91000 = 2.7e-4 of the total 100-yard path length. So the probability of the bullet and the raindrop being in the same place at the same time is 0.07*2.7e-4 = 1.9e-5, or 1 in 54,000. Ergo, there is no need to worry about a bullet encountering a raindrop under these conditions.
Feel free to recalculate for other rain intensities and drop sizes.
The basic information on rain can be found here: http://www.shorstmeyer.com/wxfaqs/float/rdtable.html
If we assume a light rain (2.5mm/hr, 2mm diameter raindrops traveling at 6.5m/sec = 23.4e6mm/hr), the volume of a single raindrop is 4.1mm^3, and the number of raindrops in a column of air 1mm^2 at the base * 1hr tall can be calculated as 2.5mm/hr / 4.1mm^3 = 0.61. The density of raindrops in the air is, therefore, 0.61/23.4e6 = 2.6e-8 raindrops/mm^3. The volume of a 6mm bullet's path over 100 yards (= 91m = 91000mm) is pi*3mm^2*91000 = 2.6e6mm^3. On average, then, there are 2.6e-8 * 2.6e6 = 0.07 raindrops in the bullet's path. Put another way, there will be a raindrop (or at least part of a raindrop) in the bullet's path in 1 out of every 14 shots or so.
But the bullet doesn't occupy its whole path at the same time. A bullet 25mm long occupies 25/91000 = 2.7e-4 of the total 100-yard path length. So the probability of the bullet and the raindrop being in the same place at the same time is 0.07*2.7e-4 = 1.9e-5, or 1 in 54,000. Ergo, there is no need to worry about a bullet encountering a raindrop under these conditions.
Feel free to recalculate for other rain intensities and drop sizes.
CatShooter
tobybradshaw said:
That works for me
In nearly 25 years of competitive shooting, I have seen one raindrop hit through the spotting scope. It was a light drizzle, the hit created a grapefruit size mist for a split second. The bullet impacted inside the group at 1000 yards.
I think both theories could be fully operational, a drop that hits the shockwave obliquely may just slide off without any visual indication, but the 1 in 54000 that gets hit dead center gives a visible puff of vaporized water.
As others have noted, keep the ammo, chamber and bedding dry and you should be ok shooting in the rain.
Ray Gross
I think both theories could be fully operational, a drop that hits the shockwave obliquely may just slide off without any visual indication, but the 1 in 54000 that gets hit dead center gives a visible puff of vaporized water.
As others have noted, keep the ammo, chamber and bedding dry and you should be ok shooting in the rain.
Ray Gross
CatShooter
iron308 said:
A rain drop cannot slide off of a shock wave - it is not a piece of window glass. The shock wave travels at almost 1,100 fps, rain drops fall at 30 feet a second. The shock wave passes through the rain drop(s)... all of them.
CatShooter
Webster said:
Vapor trails are caused from what happens after the bullet passes - the shock wave does not get in front of the bullet - it is formed on the nose and falls behind it.
CatShooter
iron308 said:
... exactly what I was saying.
That is the compression wave from the pistol shot - it is NOT the shock wave from the bullet - the bullet is not making that wave.
You need to know how to read these things.
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