Humidity vs handloading

[sig220mw]

This summer I worked up some loads for a couple of revolvers and they worked really well. It was very dry here this summer. I recently loaded the same stuff up and have not had the same accuracy. I talked to a gent at the range and he said it was probably due to the humidity which has been relatively high lately.

Any of you have similar experience? I usually load in my garage but because of this I'm loading the powder into my cases in the house instead. It seems to have helped some but the relative humidity is still high and I am not getting the same results that I did this summer.

I understand how hot weather versus cold effects powder pressures etc.
I am just wondering about humidity also and what to do or if there is anything that actually can be done.

For instance do I need a summer load and then a winter load?

 

[rcmodel]

NO.

I can't imagine humidity having any effect on powder if it is kept sealed in the factory container until you pour it into the powder measure. Then put it back in the factory container when you get done using it.

Only if you left it set in the powder measure for several days would it have a chance of picking up enough excess moisture from the air to have any noticeable effect.

I do believe I would look for some other reason to blame the poor accuracy results on.

rc

 

[sig220mw]

Thanks RC. I didn't know about how badly powder may or may not absorb moisture and at what rate if at all. I do keep mine closed up tight and in a closet in the house. I don't let it sit out and I dip it out of a small cup with a spoon and finish it off with a trickler.

 

[rcmodel]

Nitrocellulose / smokeless powder is not water soluble in the first place.

Primer compound is, and is mixed wet to avoid explosions, and then dried of all moisture after the primer is completed.

Powder is manufactured wet using Ether or other volatile solvents to dissolve it, then it is dried of the solvents after the grains are formed.

The worst that can happen to powder in high humidity is it can pick up enough mosture to change your charge weight on the scale very very slightly.

But again, you would have to leave it out exposed to open air many hours or days to have even that happen.

rc

 

[woodsoup]

The thick and thin of it.

I believe your problem is due to atmospheric conditions. The "wetter" the air that your bullet is traveling through, the denser that air is (more resistance to the bullet) the bullet will behave differently. The opposite is true for less humidity= "thinner" air.

 

[Walkalong]

Loading in high humidity vs low humidity has such a small affect you will never see it in your handgun loads unless you are some kind of world class shooter, and even then I doubt it. In Benchrest we could see it sometimes, but that is a whole different application with extremely stringent parameters needed to win. (N-133 did not mind high humidity, where TAC did TAC is still a very good powder though))

 

[USSR]

The "wetter" the air that your bullet is traveling through, the denser that air is (more resistance to the bullet) the bullet will behave differently. The opposite is true for less humidity= "thinner" air.

Actually, it's just the opposite. A bullet meets less "resistance" and will drop less in high humidity.

Don

 

[Walkalong]

Interesting, and the long distance shooters would definitely know. I'll file that good piece of info in the back of my head. (Where hopefully it will stay) At 100 & 200 I never saw a difference, but maybe I just wasn't good enough.

 

[Afy]

Well according to the gospel of Jack Neary it does make a difference. Watch his informative videos on You Tube.

My take is that it is possible that condensation can form on the granules, though not be absorbed. The overall effect I reckon may be under 0.1 grains on an average of lets say 30 grains or thereabouts. Is it enough to make a difference? Who knows certainly not me.

 

[GaryL]

Even plastics are hygroscopic, meaning they will absorb some % of moisture. Can't say what the difference would be with powder, but I doubt it would exceed more than 1%-2% by weight - so maybe a tenth or two in 20gr. A good load wouldn't be affected by it.

We see a fair amount of humidity change here, and it seems like letting a powder sit in the hopper a few days between sessions in the humidity will tip the load slightly higher on a beam, but to prove it I'd have to keep meticulous records and follow rigorous methodology.

from Wikipedia

Many engineering polymers are hygroscopic. These include: nylon, ABS, polycarbonate, cellulose, and Poly(methyl methacrylate).

Other polymers, such as polyethylene and polystyrene, do not normally adsorb much moisture, but are able to carry significant moisture on their surface when exposed to liquid water.[1]

Type-6 nylon can absorb up to 9.5% of its weight in moisture.[2]

 

[Tom609]

Actually, it's just the opposite. A bullet meets less "resistance" and will drop less in high humidity.

I don't know about a bullet, but when I ride my bike (bicycle kind), I have a noticeably harder time cutting through humid air than I do dry air. Maybe I'm misunderstanding something. It wouldn't be the first time

 

[USSR]

From a USAToday article:

Humidity and air density

Most people who haven't studied physics or chemistry find it hard to believe that humid air is lighter, or less dense, than dry air. How can the air become lighter if we add water vapor to it?

Scientists have known this for a long time. The first was Isaac Newton, who stated that humid air is less dense than dry air in 1717 in his book, Optics. But, other scientists didn't generally understand this until later in that century.

To see why humid air is less dense than dry air, we need to turn to one of the laws of nature the Italian physicist Amadeo Avogadro discovered in the early 1800s. In simple terms, he found that a fixed volume of gas, say one cubic meter, at the same temperature and pressure, would always have the same number of molecules no matter what gas is in the container. Most beginning chemistry books explain how this works.

Imagine a cubic foot of perfectly dry air. It contains about 78% nitrogen molecules, which each have a molecular weight of 28 (2 atoms with atomic weight 14) . Another 21% of the air is oxygen, with each molecule having a molecular weight of 32 (2 stoms with atomic weight 16). The final one percent is a mixture of other gases, which we won't worry about.

Molecules are free to move in and out of our cubic foot of air. What Avogadro discovered leads us to conclude that if we added water vapor molecules to our cubic foot of air, some of the nitrogen and oxygen molecules would leave — remember, the total number of molecules in our cubic foot of air stays the same.

The water molecules, which replace nitrogen or oxygen, have a molecular weight of 18. (One oxygen atom with atomic weight of 16, and two hudrogen atoms each with atomic weight of 1). This is lighter than both nitrogen and oxygen. In other words, replacing nitrogen and oxygen with water vapor decreases the weight of the air in the cubic foot; that is, it's density decreases.

Wait a minute, you might say, "I know water's heavier than air." True, liquid water is heavier, or more dense, than air. But, the water that makes the air humid isn't liquid. It's water vapor, which is a gas that is lighter than nitrogen or oxygen. (Related: Understanding water in the atmosphere).

Things aren't always as they seem.

Don

 

[WNTFW]

Water Vapor is less dense than air. High humidity lets the bullet go easier through the air.

I was a racing cyclist for some years.
Bicycle riding has some differences. Air resistance build very quickly after 20-22 mph for a cyclist. Try to maintain 24mph for a 10 mile time trial now try 26 or 27. Energy level goes up exponentially to road speed. Trying to breath humid air is probably more of what causes the perception.

 

[turbo]

This back and forth is all well and good, but for the sake of guys like Me who have told their darling little wife's " My reloading stuff has to be kept in a low humidity area Dear, thats why i'm using the spare bedroom!" Lets settle this up in our favor! LOL

 

[GaryL]

This back and forth is all well and good, but for the sake of guys like Me who have told their darling little wife's " My reloading stuff has to be kept in a low humidity area Dear, thats why i'm using the spare bedroom!" Lets settle this up in our favor! LOL

Subjecting powder to environmental extremes ages it. If we get into the subject of powder going bad, she will want it stored in a shed on the far corner of the property.

 

[MCMXI]

This summer I worked up some loads for a couple of revolvers and they worked really well. It was very dry here this summer. I recently loaded the same stuff up and have not had the same accuracy. I talked to a gent at the range and he said it was probably due to the humidity which has been relatively high lately.

Maybe the humidity is affecting YOU! I'm not being facetious. How do you feel when shooting on humid days? How is your grip? Are your hands moist?


As for the discussion on humidity, while it's true that humid air is less dense than dry air, the difference is so negligible that for all intents and purposes, and as far as the bullet is concerned, there's no difference between saturated air and dry air. Air temperature and atmospheric pressure have a significant effect on air density, not humidity. Humidity affects us and how we feel. As the humidity increases, our cooling system (perspiration) becomes less efficient which makes us uncomfortable.

 

[Tom609]

Things aren't always as they seem.

USSR, you also remind me why I went into social services.

WNTFW, interesting point. Thank you both.

 

[ranger335v]

"From a USAToday article: Quote: Humidity and air density..."

THAT is highly interesting and totally counter-intuitive, but I remember enough about the gas laws and chemistry from high school in the 50s to understand why it's true.

 

[Tom609]

There's my problem. I'm a product of the 60s. I can't remember squat.