Rain

Zey

Zey

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So, I've shot in the rain many times with both my 22 and my 223 and seen zero change. But, I'm not shooting long distance, just 100-300y.

I've read a few articles but there's nothing definitive saying that rain does affect the flight of the bullet. It mostly speaks often of visibility issues. Humidity during the rain is obviously a factor and can be accounted for. And of course, water in the bore would affect things too, but I'm generally shooting out of a roofed enclosure.

My thoughts is that a super sonic bullet would have a pneumatic shockwave riding in front of it pushing water out of it's way... yet I'm really uncertain of it as it's just a theory I thought up.
 
Aside from the wind that comes with rain, and the frequent changes in direction, including downbursts that can accompany thunderstorms the main issue is air density, that is a direct result of humidity. I doubt you will notice much effect of this at short distances.
 
Zey said:
My thoughts is that a super sonic bullet would have a pneumatic shockwave riding in front of it pushing water out of it's way... yet I'm really uncertain of it as it's just a theory I thought up.
Click to expand...

Actually, the shockwave follows the tip of a supersonic projectile. ;)
 
It follows that a wet bullet from a wet barrel will print differently on a target then a dry bullet fired from a dry barrel. I read an article years ago which included some complicated math formulas to support the premise. But I'm not aware of any formula or rule of thumb for sight adjustment for shooting in the rain, as there is for shooting in the wind. If I recall the article correctly, it suggested that the film of water on the bullet in the barrel was the cause for the change of zero, not the impact with rain drops.
 
Yes Boomer, that is consistent with my real life findings.

Quite a grey area this rain thing. One thing is for sure, while shooting in the rain I know I can walk down to see the paper anytime I want... cause the range is vacant.
 
I love shooting in rain. Rain - unlike wind flags - never lies.

I find you tend to have more elevation issues, likely due to the high humidity and the fact there is a persistent down-draft along a bullet's trajectory.
 
Even at 1000 yards, rain has no real effect. I haven't done a huge amount of shooting in the rain, but I have done my share, and I have never personally seen a shot do something "strange" that could only be explained by "it must have hit a raindrop".

It turns out that the actual density of raindrops in the air is very low - to the point that a bullet will almost never touch a raindrop during its trip to the target.

If a bullet does strike a raindrop, it will affect its trajectory. The amount of deflection will be related to how off-centre the hit is, and the ratio of the bullet's mass to the raindrop's mass.

BTW rain doesn't fall at 120mph (that's the freefall speed of a human in a horizontal attitude). Larger raindrops fall faster than smaller raindrops, at a speed that is on the order of a few metres per second.

Often a drop in air temperature happens when the rain starts to fall. This won't have much affect at short and mid ranges, but at 1000 yards having a one MOA elevation change due to the air being cooled by the rain is not out of the question.
 
Obtunded said:
I love shooting in rain. Rain - unlike wind flags - never lies.

I find you tend to have more elevation issues, likely due to the high humidity and the fact there is a persistent down-draft along a bullet's trajectory.
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A rain drop in the end of your barrel will cause wild shots, mostly vertical way out of your groups.

NormB
 
I wonder if there's a difference for shooters from a republic(eg USA) where there is no 'reign' or if you are shooting from horseback with a loose 'rein'.
 
Raindrops 22fps (Handbook of Firearms and Ballistics B. Heard)
Humidity has very little effect on ballistics.
Someone else's math:


Lets say that:
the rain storm drops one inch of rain in two hours
a raindrop is 1/100th of a ml (pretty small for that type of rain, I'd expect, but we are being cautious here)
those raindrops fall at 25 mph
That those raindrops are infinitely small (makes them hard to hit)
That you are shooting a .3" diameter bullet
At 1000 yards

So, the flight path of the bullet has a volume of 41,000 cm^3
And a cubic centimeter of air contains 2.85*10^-5 raindrops at any given point in time
So the average bullet encounters 1.2 raindrops on it's way to the target... over 1000 yards... in an incredibly dense rainstorm of unusually (?) small raindrops.

Mind you, hitting water at 2500fps might be dramatic. Shockwaves pushing the raindrops away, you still have Newton's Third Law of Motion.
 
Toomanyguns said:
Acid rain is known to dissolve bullets as they fly through the air.
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Acid rain :D I have'nt heard that in years. Its an oldie but a goodie.
I'm glad they stopped inventing problems with the weather to get us all worked up over nothing. Those were the days. :D
 
Juster said:
Raindrops 22fps (Handbook of Firearms and Ballistics B. Heard)
Humidity has very little effect on ballistics.
Someone else's math:


Lets say that:
the rain storm drops one inch of rain in two hours
a raindrop is 1/100th of a ml (pretty small for that type of rain, I'd expect, but we are being cautious here)
those raindrops fall at 25 mph
That those raindrops are infinitely small (makes them hard to hit)
That you are shooting a .3" diameter bullet
At 1000 yards

So, the flight path of the bullet has a volume of 41,000 cm^3
And a cubic centimeter of air contains 2.85*10^-5 raindrops at any given point in time
So the average bullet encounters 1.2 raindrops on it's way to the target... over 1000 yards... in an incredibly dense rainstorm of unusually (?) small raindrops.

Mind you, hitting water at 2500fps might be dramatic. Shockwaves pushing the raindrops away, you still have Newton's Third Law of Motion.
Click to expand...

The trouble with this stuff is that it is only applicable when applied to long range shooting where the groups are comparatively large. I just ran a comparison on JBM to see what the difference was between 0% and 100% humidity at sea level, with a .284/150 gr Sierra fired at 2850. The difference is 2" at 1000 yards. Now a hunting bullet isn't the best choice for long range shooting, so I ran it again with a Berger .284/168 VLD at 2700 and got a difference of nine-tenths of an inch. I should have a rifle that can detect a trajectory shift of nine-tenths of an inch at 1000 yards!

If we shoot in the rain at a 1000 yard target, problems arise other than the possible defection of the bullet by a rain drop. Can the marksman see his target well enough for proper sight alignment? Does discomfort, particularly cold, effect his marksmanship? If the bullet's impact with a rain drop near the muzzle causes slight deflection of the bullet, will the deflection be enough to take the bullet out of a 10 shot 1000 yard group, which we might anticipate being between a foot and 2 feet in diameter, even under good conditions.

While I don't have the answers, shooting in the rain does pose some interesting questions. We know that a bullet is little effected when impacting a low density obstruction, due to the bullet's spin induced stability and momentum, and a rain drop has much lower density than say a blade of grass or a twig, which can deflect it. But we also know that the deflection of a bullet is greater at long range if it is deflected by an obstruction close to the muzzle as there is more time for the error to manifest. That is why the long range shooter is more concerned with wind that is nearer to him than he is with the wind near his target. We know that the bullet is in greatest yaw immediately upon leaving the muzzle and again when it impacts a target of great density like a game animal Yaw increases the bullet's frontal area to any possible obstruction. In a rain storm, if we accept that the bullet might impact one or two drops of rain on its way to the target, we have no way of knowing where those drops of water will be when impacted by the bullet, they could be right at the crown of the muzzle, they could be near the target, or it could be at some intermediate point. Because the shock-wave of a typical match style rifle bullet comes off its ogive rather than it's nose, the rain drop probably will make contact with the bullet, but even though the bullet flies in a yaw, the rain drop will not impact the heal of the bullet, because the shock wave coming off the bullet is strongest at it's base. I'll have to start paying more attention to what happens when I shoot in poor weather.
 
Yup, I expect stability is the big thing.
Because the bullet is traveling 100 times faster than the raindrop, the bullet will hit the side of the raindrop, rather than the raindrop landing on top. Since the bullet won't hit the exact centre of a perfectly spherical raindrop, there will be a tendency for the bullet to deflect, but perhaps stabilization fixes that. Or shockwaves reduce the effect anyway.
Any effect on accuracy would be highly random, so it would be hard to design an experiment to test the effect. Unless 1% of your shots take a huge detour.
 
Rain, like snow and mirage allows one to "see" the wind. The apparent angle of the falling rain or snow is a perfect anaology of the wind strength and angle.

If a fast moving low pressure moves into the area, the falling atmospheric pressure will cause the group to shift upwards. I have seen this only once, during a long and slow target rifle match. A number of us noticed our group shift upwards by 1 1/2 minutes over the hour of shooting. (No rain, just a low pressure area moving in.)

I have never seen any efect of the rain on the bullet, but I have seen a change in MPI of wet ammo vs dry ammo. Those of us who shoot in the rain have technique to keep the ammo and action dry.

One thing we do is keep the barrel level or pointed down between shots, so water does not get into the barrel. That does cause problems.
 
Boomer said:
We know that a bullet is little effected when impacting a low density obstruction, due to the bullet's spin induced stability and momentum, and a rain drop has much lower density than say a blade of grass or a twig, which can deflect it. .
Click to expand...

Grass and twigs float in water, thus a raindrop is denser than either of those.

NormB
 
Absolutely yes, bullets hit rain, a lot. Most people do not shoot in what we call a normal rain. If its just a very light rain we tend to stick with it but really, when it actually rains we come back another day. You can hear the distinctive sound if conditions are right. The effect on the path of the bullet is almost negligible.
 
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