Rain -- Does it affect POI?

[Syncrowave]

I'm sure it's been discussed and I tried searching but couldn't find anything...

How much does light rain typically affect bullet trajectories at up to say 200 yards?

I need to work up some loads this week for my 6.5/284 and they're calling for rain all week. I won't be shooting in a downpour, but was curious what you all have found when shooting similar cartridges in light rain / drizzle.

Does it make enough of a difference at 200 yards to worry about?

Again, this isn't for score or group size so much as identifying nodes for further exploration and development...

Thanks.

 

[dragman]

All my competitive shooting is done at 850 yards and over. I have shot in the rain and sun and at that distance I don't think rain has any baring POI at all. In fact my absolute favorite conditions are a light steady rain

 

[Immike]

There was a article once in PS magazine about this. The author said that moisture reduced the air density.

 

[jonbearman]

I cant believe that rain wouldnt affect point of impact.At bullet speed it would seem like it would be like pushing pebbles out of the way.

 

[timeout]

I have not delved all the way into ballistic aps as yet but, would not rain equal 100% humidity? If so a ballistics program could be figured out at different humidity levels to formulate a theoretical number. I have not personally tried shooting targets in the rain, but would give Dragman the benefit of the doubt. The target doesn't lie.

 

[dragman]

I couldn't swear it doesn't as all my rain shooting is 100 yards or 850+ and on steel targets not paper. so slight shifts in impact might not be detected or could be attributed to wind.

 

[ar15topgun]

I know it's not a good thing to chamber a wet round and fire it. Sometimes things get pretty interesting when you do.

 

[CatShooter]

I cant believe that rain wouldnt affect point of impact.At bullet speed it would seem like it would be like pushing pebbles out of the way.

You cannot hit rain drops - there is sooooo much air, and sooooo few drops of rain, you have a better chance of winning the power ball than hitting a rain drop. If you can clearly see the target, you cannot hit a drop/

Light rain is also my most favorite shooting condition - it is perfect - zero wind, zero mirage!

 

[DukeDuke]

I have not seen any shift of poi out to 1000y , raining or not

 

[bheadboy]

a bullet at speed has an air shock wave in front of it, you will not hit a rain drop, secondly, often in light rain the humidity drops as the moisture collates, thus the ? of more dense air is a non issue.

love shooting in the rain light or medium with wind, you can really see where the wind is going.

Bob

 

[pdhntr]

How much does light rain typically affect bullet trajectories at up to say 200 yards?

I need to work up some loads this week for my 6.5/284 and they're calling for rain all week. I won't be shooting in a downpour, but was curious what you all have found when shooting similar cartridges in light rain / drizzle.

Does it make enough of a difference at 200 yards to worry about?

Late last fall I was testing a new 25-06 with 115 Nosler Partitions. I was shooting from my concrete bench (using bags) across my 200 yard range. During load development it was, what I would call, drizzling. I found a load and the last two shots were almost touching at 200 right on the bull. I took a break to load up several more to make sure of the load, and during that time it started to rain. It's hard to describe exactly, but it wasn't light rain, and it wasn't heavy rain.

I shot the newly loaded ones anyhow, and when I checked the target the three were spread out about 4 inches low from the bull. I quit for the day.

The following day it was not raining, I loaded up several more just like the others, and shot them. They went right into the bull grouping with the original two.

This is just one occurrence, not scientific proof by any means. Take it for what it is worth.

Jim

 

[pdhntr]

One more thing I would like to mention though.

Cool air sinks and warm air rises. It is entirely possible the rain caused a "down draft" so to speak.

Jim

 

[letronshootit]

I haven't seen a change in poi from 850 to 1,000yd with either 25-06 or 6br on steel silhouettes. No changes were needed for elevation. The rain is nice if the wind isn't roaring. Not sure why Jim had a problem, I was using 115 bergers in the 25-06.

 

[Syncrowave]

Thanks, fellas. Sounds like I can ignore any rain for my purposes.

 

[Syncrowave]

a bullet at speed has an air shock wave in front of it, you will not hit a rain drop

Even at supersonic speeds? I thought air shock waves traveled at the speed of sound.

 

[lrgoodger]

Not sure what the condition that caused it, whether denser air because of increased water content, barometric pressure or whatever, but I had the same experience as Jim. We were shooting a 200 yard match and the rain started falling on the fifth or sixth of the 20 shot match. It was a steady, light rain and POI immediately dropped and inch and a half when the rain started. I held that much high on the remainder of the shots and did pretty well. After the match I asked other shooters if they had to raise their point of aim and they all said the same thing, yes, they did.

Also, the same day during the rim-fire matches (which I don't shoot), I was watching one of the youth shooters. On one of his shots I noticed a puff of vapor about six feet in front of his muzzle when he fired. I began watching the air just in front of the bench and I saw no less than THREE bullet/raindrop impacts. It was really kind of neat. There would be a puff of mist that quickly blew away as the bullet hit the droplet. I was surprised because I had read the same thing about the chances of hitting one being nil, but it is not so. The slower velocity of the .22 rim-fire ammo probably makes it more likely than for a center-fire round.

 

[CatShooter]

a bullet at speed has an air shock wave in front of it, you will not hit a rain drop, secondly, often in light rain the humidity drops as the moisture collates, thus the ? of more dense air is a non issue.

love shooting in the rain light or medium with wind, you can really see where the wind is going.

Bob

The shock wave is NEVER in front of the bullet - it spreads out and back from the nose (and other physical changes) at an angle which is related to the speed - when the bullet speed is below the speed of sound, there is no shock wave.

 

[243Mendoza]

The shock wave is NEVER in front of the bullet - it spreads out and back from the nose (and other physical changes) at an angle which is related to the speed - when the bullet speed is below the speed of sound, there is no shock wave.

A normal shock (normal meaning perpendicular to the flow) is in front of the projectile/aircraft. With a sharp-nose object, the extent of the normal shock will be small relative to the oblique shock (see DMoran schlieren pic of shocks around a bullet).

 

[dmoran]

On another note, there is always moisture in the air..... just typically more when raining, fog, or snowing.
The higher the humidity, the more moisture in the air, and the easier it is to see the "vapor trail".
D

 

[CatShooter]

The shock wave is NEVER in front of the bullet - it spreads out and back from the nose (and other physical changes) at an angle which is related to the speed - when the bullet speed is below the speed of sound, there is no shock wave.

A normal shock (normal meaning perpendicular to the flow) is in front of the projectile/aircraft. With a sharp-nose object, the extent of the normal shock will be small relative to the oblique shock (see DMoran schlieren pic of shocks around a bullet).

I have taken thousands of Schlieren photos and shadow graphs at Columbia University, documenting small particles of coal at high velocity in methane and helium.... and I design systems to take these photos.

The shock wave never gets in front of the bullet, except when the bullet just slips below the speed of sound.

The wave is generated on contact with the tip, and every irregular surface on the projectile.

At the speed that bullets move when making shock waves, drops of water cannot get out of the way.