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Thread: Powder moisture content

  1. #1
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    Oct 2011
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    Asuncion, Paraguay

    Powder moisture content

    https://www.vihtavuori.com/know-powder-moist-content/

    "Variations in moisture content change the burning rate of a powder and thereby chamber pressures and muzzle velocity. The moisture content of the N100 and N300 series powders is usually around 1 %, the N500-series’ normal moisture content is 0.6 % because of the added nitroglycerine.

    So what difference does moisture content have? Here’s an example. In a test, a powder sample was dried by heating it, losing about 0.5 % of its weight. Cartridges were then loaded with the dried powder and fired using a pressure gun. Chamber pressures and muzzle velocities produced by these special cartridges were compared to those produced by cartridges loaded with untreated powder. (The powder charge and bullet were of course the same in both sets of cartridges.)

    Comparing results showed chamber pressures increased from 320 MPa to 355 MPa with the dried powder, and the muzzle velocity increased accordingly from 770 m/s to 790 m/s (2526 to 2592 fps). And note, this is only one example, of one caliber and loading. The difference might be much higher depending on the cartridge and loading combinations.

    What does this tell us? Well, it seems we need to forget the old saying “Keep your powder dry”! Instead, focus on proper powder storage, at a temperature below 20°C / 68°F and humidity between 55-65 %. Safe reloading everybody!"

    Great advice! I have lots of old podwer, and live in a subtropical country... always good to work up a load, again, after a long while.

  2. #2
    Good post. What is everyone doing w storing their powder?

    I usually leave the powder in the hopper but have been noticing from day to day that I have to keep adjusting the powder bar just to get back to the same charge weight. Im guessing its probably better to re-bottle after each session?

  3. #3
    Quote Originally Posted by PhillySoldier View Post
    Good post. What is everyone doing w storing their powder?

    I usually leave the powder in the hopper but have been noticing from day to day that I have to keep adjusting the powder bar just to get back to the same charge weight. Im guessing its probably better to re-bottle after each session?
    The hopper is not air or moisture tight which will cause clumping and degrade the quality. Powder is also acidic and will damage the hopper over time.

    I keep my powder in it's factory container and firmly close the lid and keep it on a shelf out of direct sunlight. If you want to go the extra step you can store the container in a zip lock bag or ammo can.

  4. #4
    Member Les Pepperoni's Avatar
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    Quote Originally Posted by Artemas2 View Post
    The hopper is not air or moisture tight which will cause clumping and degrade the quality. Powder is also acidic and will damage the hopper over time.
    Titegroup is great of melting Hornady LNL hoppers!

    The Dillon hoppers just get discolored...

    Personally, I only put as much powder into the hopper as I know I'll load. I'll dump the rest - usually a negligible amount - back into the keg until the next session and store in an "locker"... I'm not too worried, but maybe I've got to start keeping tabs on this.

  5. #5
    Site Supporter
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    Canton GA
    Living in Georgia, I only comply with this about 3 months per year even in the dark, cool corner of the basement: "Instead, focus on proper powder storage, at a temperature below 20°C / 68°F and humidity between 55-65 %". So far, no issues with my powder (or primers).

  6. #6
    Site Supporter
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    Jul 2017
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    Texas
    Keeping powder in an air tight container may be the most important storage criterion because moisture in the powder then can't pass into the atmosphere. The water is not part of powder's molecular structure so the process is not sublimation where a solid changes into a gas as seen in moth balls. A good example would be soil moisture which evaporates into the atmosphere. Funeral homes and morgues cover bodies in coolers with plastic which is a barrier slowing down water loss in the form of water vapor escaping tissues. Tight caps on powder serve this same purpose.

    Extruded powders are extruded under water. Some powder manufacturers store archival powder used for comparisons under water and then dry it out for use. Alliant's Unique is an example. When having powder subjected to flooding like a basement water leak, some have spread it out for drying and reusing afterwards.

    About storing smokeless powder. Military arsenals would store 100's of tons outside in igloos or even in large piles. Yes, it's a great idea to observe manufacturer recommendatons for storage. My opinion is that we need not fret about leaving powder in a measure hopper for a few days. But doing so may degrade the measure's plastic. It also may cause the person to pour it back into a wrong container should he forget which powder it is. This does happen. Some reloaders are still using WW2 surplus powder bought in the 50s and 60s. In 1977 I shot 2000 rds of .45 ammo through a police dept Thompson. The ammo was made in the 1920s. There were no misfires. I have a batch of military .45 ammo made in 1962. It shoots great. I could give other examples.
    Last edited by willie; 07-31-2018 at 12:01 PM.

  7. #7
    King of Craft Clusterfrack's Avatar
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    Redneck wonderland

    Powder moisture content

    A while ago I measured the weight of H4350 left at ambient humidity for a month vs kept in a container with desiccant. No measurable difference.
    Last edited by Clusterfrack; 07-31-2018 at 12:09 PM.
    "BJJ is sort of like nonconsensual yoga"
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  8. #8
    So they changed equally or both had no change at all?

  9. #9
    King of Craft Clusterfrack's Avatar
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    Quote Originally Posted by PhillySoldier View Post
    So they changed equally or both had no change at all?
    No change.
    "BJJ is sort of like nonconsensual yoga"
    "You don’t really graduate from certain problems or certain things… like you always have to work on trigger control and pulling the trigger straight. " --Ben Stoeger 1/24/2018

  10. #10
    Mr. Shovel Lover Hambo's Avatar
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    Quote Originally Posted by TiroFijo View Post
    Instead, focus on proper powder storage, at a below 68°F and humidity between 55-65 %.
    AC keeps the humidity down to less than 50%, but <68°F isn't going to happen.
    John Wick didn't kill all those people because they broke his toaster.-MickAK

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