What effect does humidity have on accuracy?

[Jerry Snyder]

We shoot each week here in Arizona (Ben Avery Range)., It only rains like 5 or 10 days a year. It rained last night and the temps this morning were in the 40. For us Arizonans, that is like Heck freezing over. We did shoot our 22LRs today we we noticed neither one of us had much luck in the accuracy department. Before I got my stuff on the bench, I heard many other shooters complaining about something or the other messing with their accuracy. Your thoughts: Bad day of shooting or is there really something to humidity in the air causing some irregularities in accuracy? Thanks

 

[6Creed73]

When I was shooting a lot of PRS, I shot in all kinds of conditions. I can't say simply having humid air had any affect on my precision. In fact, in my experience, I did better when it was somewhat humid because there was much less mirage.

 

[TheDream]

Funny enough, I just actually was thinking about this the other day. We just had a whole week of dense fog where you could just barely see the target out to 50 yards. There was absolutely no wind to speak of. I ended up shooting the worst targets of the year for me. I had 5 or 6 fliers that ended up being 25s on the ARA unlimited target which killed my morale. I want to say that the humidity definitely does affect accuracy, but that might just be me trying to come up with excuses.

 

[6Creed73]

Funny enough, I just actually was thinking about this the other day. We just had a whole week of dense fog where you could just barely see the target out to 50 yards. There was absolutely no wind to speak of. I ended up shooting the worst targets of the year for me. I had 5 or 6 fliers that ended up being 25s on the ARA unlimited target which killed my morale. I want to say that the humidity definitely does affect accuracy, but that might just be me trying to come up with excuses.

I'd put fog in a different category than humidity...its hard to be accurate if you can't see the target

 

[dutch14]

The bullet strikes the target lower and the wind has more effect because the air is denser. I would also put fog in a different category.

 

[VLNBYR]

Actually water vapor is lighter than air, that's why clouds float. Fog is intense water vapor in the air, essentially a cloud at ground level.

 

[gunsandgunsmithing]

Actually water vapor is lighter than air, that's why clouds float. Fog is intense water vapor in the air, essentially a cloud at ground level.

This! If the air is dense, it has less room for moisture.

 

[VLNBYR]

Cold air is more dense than warm air. You see this at ranges where there is a wooded hillside and as the day progresses you will get a "wind" condition as the cooler air in the woods sinks down the hillside and out onto the range. Kettlefoot in Va is a prime example.

 

[Bill Norris]

According to B R shooters humidity levels does affect powder burn. Considering that line of thinking it is hard to imagine it not affecting accuracy.

 

[Straightshooter1]

We shoot each week here in Arizona (Ben Avery Range)., It only rains like 5 or 10 days a year. It rained last night and the temps this morning were in the 40. For us Arizonans, that is like Heck freezing over. We did shoot our 22LRs today we we noticed neither one of us had much luck in the accuracy department. Before I got my stuff on the bench, I heard many other shooters complaining about something or the other messing with their accuracy. Your thoughts: Bad day of shooting or is there really something to humidity in the air causing some irregularities in accuracy? Thanks

The more water vapor there is in the air the less dense it is. Less dense means less resistance, which of course can effect trajectory and how any wind might effect the bullet's flight. But, humidity is only one factor at play as temperature, altitude and barometer readings all work together effecting the flight of the bullets. Density Altitude is what you want to pay attention to as it takes into account those factors.

Humidity can effect powder burn is one is loading at the range where the powder is exposed to the environment for any length of time. For pre-loaded ammo, there can be some effect if there's enough altitude to cause an exchange of the outside condition with the cartridge's interior condition; the longer they're exposed the more that's exchanged and the bigger the difference the faster the exchange (unless you're sealed the primers and necks to keep that from happening).

 

[Bill Norris]

The more water vapor there is in the air the less dense it is. Less dense means less resistance, which of course can effect trajectory and how any wind might effect the bullet's flight. But, humidity is only one factor at play as temperature, altitude and barometer readings all work together effecting the flight of the bullets. Density Altitude is was you want to pay attention to as it takes into account those factors.

Humidity can effect powder burn is one is loading at the range where the powder is exposed to the environment for any length of time. For pre-loaded ammo, there can be some effect if there's enough altitude to cause an exchange of the outside condition with the cartridge's interior condition; the longer they're exposed the more that's exchanged and the bigger the difference the faster the exchange (unless you're sealed the primers and necks to keep that from happening).

On a video segment (Believe the Target) by Erik Cortina discussion with Bryan Litz this was part of that discussion. Bryan reported that he saw 200 fps difference in his pre-loaded ammo from the time of loading until time of actual firing at a different location due to these factors.

 

[grauhanen]

If humidity negatively affects accuracy, it must cause all rounds to somehow fly less accurately to the target. The alternative is that humidity affects only some rounds in a box, but not all.

Is there reliable, quality evidence about the relationship between higher or lower humidity levels on ammo performance?

 

[STORM2]

#60 - Humidity Effects on Smokeless Powder - The Science of Accuracy

thescienceofaccuracy.com

Take notes, there may be a test.

 

[TRSR8]

Well folks, I’ll tell you some of the absolute best RFBR targets I ever shot were in a nice, gray, light drizzle, low pressure front.
zero, mirage, generally light but constant wind…., I pray for those days.

 

[PWNolan]

Well folks, I’ll tell you some of the absolute best RFBR targets I ever shot were in a nice, gray, light drizzle, low pressure front.
zero, mirage, generally light but constant wind…., I pray for those days.

Yep, light fog to start. Then it turned into light drizzle. Both rifles I shot that day shot well. Unfortunately, I haven't seen one of those days since I moved to TX awhile back

 

[Terrykuz]

I'm in Pennsylvania, and 40 is kinda warm this time of year.
Anyway, I see below 50F or so I get a big change in performance compared to higher temps. Funny but I was just telling my wife how testing ammo now (low 30s) is not so valid for upcoming (March) silhouette season. I just checked my phone, and humidity is 69%, and winter is known as drier here. Anyway for discussion, and as a guess, I'm guessing temperature more than humidity. Generally it is always humid here compared to Arizona.
I bet at the first match shooters will be blaming the cold on ammo performance, something I hear every year. Never heard anyone blame humidity, but like I said this place is pretty wet. 41 inches a year, 30 year average.
Best silhouette scores are shot here in cloudy drizzle or light rain. I'll guess that is due to better optics due to flat light and certainly less wind. Another thing always said here.

 

[doclu60]

Yep, light fog to start. Then it turned into light drizzle. Both rifles I shot that day shot well. Unfortunately, I haven't seen one of those days since I moved to TX awhile back

Pat, back when you were still up north Gunner was at his range and I was at my range. Moist, kind of foggy conditions at both. We were both shooting groups for one of the group games on RFC. We talked a few days later and we both had exceptional results. My best ARA day ever, was in similar conditions.

Scott

 

[SecondsCount]

I'm not sure on the humidity part, but some 22LR ammo becomes less accurate for me in colder weather.

 

[dstoenner]

With humidity comes mirage and the target dances. It is hard to find a consistent firing point hence poorer accuracy. Happens to me with centerfire guns at long ranges like 1000 yards.

David

 

[VLNBYR]

Shooting in cold temps doesn't cause accuracy problems, it just highlights problems you already have. A good rifle and good ammo will shoot well all the time.