Shooting for accuracy in the rain.

BCRider

BCRider

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A month or so back I finally had a quiet day where I could go out with a couple of rimfire rifles and putter for sighting in and ammo testing for accuracy. Things were going along well with interesting results when I noticed that my groups were suddenly going low and opening up drastically. I then took stock of the fact that it had begun to rain very lightly. It was more than a mist or spitting but still small drops very much of the "light" sort. Not the sort which was easy to see.

It dropped my group at 25 yards by almost an inch and opened the group up from the size of a dime to about 1.5 inches just like <snap>.

So that was another good lesson. We can't expect accuracy in the rain.

Anyone else with rain vs rimfire stories? I'm curious if your experience matches mine.
 
Wooden stock? Needs to be sealed in the receiver area and the barrel channel. Any wood sealer will do. Tung oil will seal it as well.
Happens with any wood stock. The wet causes the wood to expand.
 
BCRider said:
A month or so back I finally had a quiet day where I could go out with a couple of rimfire rifles and putter for sighting in and ammo testing for accuracy. Things were going along well with interesting results when I noticed that my groups were suddenly going low and opening up drastically. I then took stock of the fact that it had begun to rain very lightly. It was more than a mist or spitting but still small drops very much of the "light" sort. Not the sort which was easy to see.

It dropped my group at 25 yards by almost an inch and opened the group up from the size of a dime to about 1.5 inches just like <snap>.

So that was another good lesson. We can't expect accuracy in the rain.

Anyone else with rain vs rimfire stories? I'm curious if your experience matches mine.
Click to expand...

I wonder if the same applies to centerfires? All of my practise time is generally during clear dry days, while hunting days are taken when you can get them, rain or shine.
 
I wondered the same thing Sunray did. I've shot my .308 in both moderate rain and hot/dry with no POI or group change. The rifle is bedded in a B&C with alu. bedding block though. Cold bore did not change, no adjustment necessary between the two days/weather. Of course its not a rimfire so its hard to say how much really applies.
 
There might be a correlation between precipitation and POI, but measuring it might also be difficult. The change in POI might be attributed to air density and resulting pressure change, but a 4 MOA change sounds strange.
My POI change from high humidity days with precipitation to drier days might be as much as 1/4 - 1/2 MOA. Insignificant really when other effects are considered.

The affect of humidity on a wooden stock, one would think would have a more protracted influence than merely at the start of a light rain. To reduce the likelihood of this - float the barrel and glass bed the action if not already done.
 
All three of us, the rifles, the ammo and me, were under the covering roof of the firing line at my club range. So the stock didn't get wet and the humidity didn't SEEM to change to a noticeable degree. It simply went from being heavily overcast, cool and calm to the same but with the light rain over about a minute or two.

I didn't bother trying this with the other two rifles since I chalked it up to the rain and figured that any chance of shooting for accuracy testing was washed away... :D But living where I do I KNOW I'll have numerous opportunities to test for the effect of rain on rimfires again. And likely sooner than I'd wish for :D

It's interesting that some of you don't notice this with the bigger center fire stuff. But given how folks love to talk about how the fast but light .17's can be deflected by a blade of grass it does make me wonder if the .22 is light enough to be affected by rain drops to notice like this. Keep it in mind for your own times when you find it starting to rain and take note of any drop in accuracy. Let me/us know for the good of the cause?
 
Last time on pest control in the rain, I didn't notice any difference on how the bullets hit.
Never really gave this any thought.
Interesting concept though.
 
I've done a lot of target shooting in the rain, shooting for groups I've never noticed any change in accuracy. I don't believe it affects it much if at all.
 
Relative humidity has a direct affect.
The rain will also create a sudden cold down draft.
When testing 22 match ammo, the temperature of test day should be correlated to match day.
At the last Mission 22 BR, there was a sudden drop of 3 degrees and the scores reflected that change for most.
 
I've read a few articles about how rain/snow can open groups up. The authors shot same rifles and same ammo in dry and foul conditions. Smaller bullets were effected more, IIRC
 
horseman2 said:
Relative humidity has a direct affect.
The rain will also create a sudden cold down draft.
When testing 22 match ammo, the temperature of test day should be correlated to match day.
At the last Mission 22 BR, there was a sudden drop of 3 degrees and the scores reflected that change for most.
Click to expand...

h2
What amount of correction to get you back on zero ? The OP is talking about a 4 MOA difference that he noticed in precipitation !

keep 'em centred
d
 
Humidity plays a major roll in accuracy based on distance
bare metric pressure changes everything .
Now 200 is so close .
The farther you go the bigger the diviation
now humidity with heat all plays big part as well as having cold or warm bullets
 
dryfire said:
h2
What amount of correction to get you back on zero ? The OP is talking about a 4 MOA difference that he noticed in precipitation !

keep 'em centred
d
Click to expand...

On the ARA target they were dropping into the 25 ring.
While it took a while to realize what was happening, it corrected almost as quickly.
There is no such warning it is happening, not at all like reading the wind.
 
horseman2 said:
On the ARA target they were dropping into the 25 ring.
While it took a while to realize what was happening, it corrected almost as quickly.
There is no such warning it is happening, not at all like reading the wind.
Click to expand...

Would that be about .5-.75 MOA ?
You need some uppy-downy boards to detect vertical air movement. Killoughs has them as do vendors on Benchrest Central. You just need to second-guess where to place them in that 50 yards.
 
Only the humid swelling of a wooden stock should make any difference, especially at a mere 25 yards. But that was a pretty fast change if so, since the OP says he and the rifle were under cover. It's kind of tempting to think the rain was just a coincidence.
 
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