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How long can you leave powder in a dispneser?

Discussion in 'Handloading and Reloading' started by CMV, Jan 1, 2012.

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  1. CMV

    CMV Member

    Dec 18, 2011
    Winston-Salem, NC
    For an auto dispensing scale, but really for anything that holds powder other than the original container. I know the clear plastic will discolor & become brittle over time from contact with powder so minimizing it is smart. But is there a need to dump back into original container if it's all going to be used within 72 hrs?

    Is the powder going to absorb moisture from the air and change characteristics?

    Will it rapidly accelerate the "aging" of the clear tube on the dispenser?

    Or if I'm using the dispenser for 2 hrs, should I have powder in it for 2:15 & that's it?

    The tube is capped, but not as tight a seal as the original container. Plus the dispenser gets opened & closed frequently while the original one doesn't so there's less exchanging of outside air in it.
  2. esheato

    esheato Member

    Apr 8, 2003
    My 650 has had powder in it for at least 10 years continuously....and I load in spurts. A thousand or two this week, then it sits for a month, then change toolheads and load another thousand or two, etc...

    Don't worry about it.
  3. FROGO207

    FROGO207 Member

    Dec 7, 2008
    Mount Desert Island Maine
    Well I have an older Lyman 55 that had to have a new plastic powder tube because I left some Unique in it for a couple days. Also it is easier to remember what was in the measure when you get done with it rather than trying to figure it out a few days later. I have 19 different types of propellant in the reloading room. Also the tighter you seal the container the less moisture moves in or out of the stuff and the more accurate the weight will remain for the remainder of the can when it is used. The newer plastics may not be bothered it seems, you going to take a chance??
  4. ColtPythonElite

    ColtPythonElite Member

    Jan 8, 2011
    I'd guess the humidity in your loading area needs to be factored in. One thing to consider aboutl eaving powder in your hopper too long is that it may etch the clear plastic hopper.
  5. oldreloader

    oldreloader Member

    Apr 24, 2009
    Magnolia AR
    I always dump mine back into the proper container after I'm done. It's easier for me to keep the right powder in the right place. Some plastics are easily discolored too.
  6. Slamfire

    Slamfire Member

    Dec 29, 2006
    From what I had read on the internet, which is a repeat of what is said in gun magazines, powder has an “indefinite” shelf life. Remember reading statements to the effect that powder lost energy as it got old, making it essentially benign.

    Then I ran into an Insensitive Munitions expert. This IM expert explained that powder deteriorates from the day it leaves the factory.

    Nitrocellulose decomposes through the reduction-oxidation process. Called Redox. The expert said “The molecular stability of the functional groups on the organic chain determine the life time of the nitrocellulose molecule.” All ionic compounds, water is the main offender because it is always in air, react with those bonds and accelerates the deterioration of the powder.

    The bottom line is that nitrocellulose is a high energy molecule that wants to become a low energy molecule.

    Heat accelerates the deterioration/decomposition of powder and the rate is directly proportional to the Arrhenius equation. If you read in the Insensitive munitions literature, you will see that they use high temperature to accelerate aging of smokeless propellants.

    Double based powders have a reduced lifetime compared with single base. Double based powders have nitroglycerin (NG) in the grain. Nitroglycerine remains a liquid and it migrates within the grain to react with the NO bonds on the nitrocellulose, increasing the rate of reduction-oxidation reaction. All ionic compounds react with those bonds and accelerate the deterioration of the powder. Rust is bad as ferric oxide is ionic. Water is ionic and it is ever present in the air.

    Because water reacts in a negative way with smokeless propellants, quality ammunition is manufactured in humidity controlled environments. Between 40% and 20% humidity. They don't go lower due to electro static discharge concerns.

    The best storage condition for powders is arctic. Cold and dry.

    Due to the migration of NG within double based powders, the surface of the grain will become rich in NG even though the total energy content of the propellant has decreased. This will cause changes in the burn rate, and can cause pressures to spike. The surface of nitrocellulose powders also change as the powder deteriorates, and it changes unevenly. This creates conditions for erratic burn rates. Burn rate instability is undesirable and can cause explosive conditions in firearms. In retrospect, this explains the “funny” retorts I experienced and the sticking cases. It is an extremely rare occurrence, but old ammunition has caused rifle Kabooms. When I discussed this with a machine gunner buddy, he said that explained the two top cover explosions he had with old Yugoslavian 8 MM ammo.

    Section from the US Army Propellant Management Guide:

    Stabilizers are chemical ingredients added to propellant at time of manufacture to
    decrease the rate of propellant degradation and reduce the probability of auto ignition during its expected useful life.

    As nitrocellulose-based propellants decompose, they release nitrogen oxides. If the nitrogen oxides are left free to react in the propellant, they can react with the nitrate ester, causing further decomposition and additional release of nitrogen oxides. The reaction between the nitrate ester and the nitrogen oxides is exothermic (i.e., the reaction produces heat). Heat increases the rate of propellant decomposition. More importantly, the exothermic nature of the reaction creates a problem if sufficient heat is generated to initiate combustion. Chemical additives, referred to as stabilizers, are added to propellant formulations to react with free nitrogen oxides to prevent their attack on the nitrate esters in the propellant. The stabilizers are scavengers that act rather like sponges, and once they become “saturated” they are no longer able to remove nitrogen oxides from the propellant. Self-heating of the propellant can occur unabated at the “saturation” point without the ameliorating effect of the stabilizer. Once begun, the self-heating may become sufficient to cause auto ignition.

    The Armed Forces have stockpile surveillance programs but each Service does theirs a little differently. If you want to see all the different tests the military uses to determine propellant characteristics, look at Mils Std 286 Propellants, Solid: Sampling, Examination and Testing to be found at https://assist.daps.dla.mil/quicksearch/.

    If you look, you will find aging tests. One common test is for powder to be kept at 65 C until it fumes. It if fumes within 30 days it is checked for stabilizer or scrapped.

    The Navy expert told me a few ways the Navy samples its powders and propellants. If the powder is outgassing nitric gas (as determined by change of color of methly violet paper in contact with the powder (Methly Violet test, or Talliani test)), the stuff is tested to see how much stabilizer is left. If the amount is less than or equal to 20%, the lot is scrapped.

    Scrapping powders and propellants with this percentage of stabilizer appears to be consistent across all services.

    Pages 5-11 of the 2003 Army Logistics Propellant Management Guide provide the protocols for testing and subsequent actions for their Stockpile Propellant Program. Basically, all propellant lots are tracked. The trigger for investigation is: "When Master Sample Stability Failure Occurs"

    The Navy expert provided 'rules of thumb' concerning when to expect problems with double based and single based propellants. The rules of thumb are: Double based powders and ammunition are scrapped at 20 years, single based 45 years. In his words “These 'rules of thumb' are particularly useful when the protocol fails. The protocol can easily fail when workmanship or good housekeeping measures are not followed during manufacture of propellant and/or rocket motor or during storage of the weapon system components, respectively.”

    The expert suggested that it is likely that surplus military powders are not on the market anymore due to liability issues. The stuff was scrapped because the military decided it was not safe to keep around anymore.

    For the home reloader, if the powder has turned red, or smells like acid, it is way beyond its safe limits.

    I am of the opinion that the reason this is not discussed in the popular gun press is because if the shooting community knew that powders had a shelf life, it might effect sales. As we all know, gunwriters are shills for the industry and for decades the shills have been reassuring us that as powder gets old, it becomes benign. I cannot see a reason why industry wants you, the shooter, to be picky about old powders and old ammunition. You might not buy, you might have reservations about buying. It is all about profits you know.

    More to read if you wish:


    This paper discusses most of what I have written, but it has a confusing section where it states that “Suddenly, propellant that has spent its entire life in a configuration that was considered inherently safe from the risk of auto ignition is now bulk packaged and stored in a concentrated mass that may be sufficient to allow auto ignition to occur.” After discussions with the Navy expert I found that the insensitive munitions community has its own myths and legends. There are groups within the IM community who promote the “5 inch” rule. The theory is that for munitions 5 inch and smaller, the thermal mass of the case is sufficient to wick away heat and prevent auto ignition. The Navy expert considers this theory to be bogus and created by self serving individuals who get cash awards when they “extend the shelf life” of propellants. Never doubt the power of greed.


    An example of powder that went bad in the can:

  7. cfullgraf

    cfullgraf Member

    Oct 19, 2010
    East TN
    I always return powder to the original container at the end of a reloading session.

    I do not want to forget what was in the measure. I do not want the plastic on the powder measure damaged by the powder.

    Finally, just in case being outside the original container for an extended time deteriorates the powder, I return it to the original container.

    BADUNAME37 Member

    Aug 10, 2008
    The longest I have ever left it in my RCBS Uniflow powder measure would have been two to three days, when I was in the middle of a large batch. I put a yellow post-it on, up under the top cover to stick in place, explaining what powder I had in there.

    My reloading area is extremely dry all times of the year, being heated in the winter and a dehumidifier running all summer so my many tools won't rust that are in the basement where everything is.
  9. Waywatcher

    Waywatcher Member

    Sep 15, 2006
    +1, that's exactly what I do.

    Post #1200, whoo hoo.
  10. Clark

    Clark Member

    Jan 3, 2003
    Where I5 meets the rain forest
    Power Pistol will etch into the green hopper of an RCBS Uniflow powder measure, overnight.

    Other powders, I have not had the problem.
  11. 4895

    4895 Member

    Mar 6, 2011
    Tucson, Arizona
    I almost always return powder to its original container. I have left it in overnight when I became too tired to return after a honey-do interruption.

    P.S. water is NOT an ionic compound. It is covalent.
  12. kelbro

    kelbro Member

    Nov 11, 2007
    Desert Southwest
  13. Pete D.

    Pete D. Member

    Sep 13, 2010

    I label the powder and charge drop weight for each hopper that is in use. For dispensers that have a single purpose or get used a lot, I leave the powder in. I have not noticed any etching on any of them.
    I have a number of progressives that I keep full and ready to go. There has been powder in those hoppers for years.
  14. Kevin Rohrer

    Kevin Rohrer Member

    May 29, 2010
    Medina, Ohio USA
    I return powder to its original container immediately after use for two reasons:

    1. It WILL yellow and damage the plastic hopper if left in it long enough.
    2. I will forget what is there and won't be able to match the powder to it container. Too many powders look similar. Big safety no-no. :what:
  15. Joatmon

    Joatmon Member

    Oct 30, 2010
    Lots of good info, with me the issue is that 72 hours in the measure can easily turn into two weeks or more with other distractions popping up to prevent getting back to the bench. The chance for a mixup increases, which is potentially a big hazard to to shooter and the firearm. The density of a powder also changes as it evaporates solvent and potentially absorbs water. Also, as stated above, double base powders (nitroglycerin and nitrocellulose) are really rough on a lot of plastics. Given time they can eat right into and dissolve the plastic. Single base powders (rifle stick powders) dont tend to cause problems as quickly. Empty the measure if possible to avoid any issues IMO.
  16. Walkalong

    Walkalong Moderator

    Nov 20, 2006
    Bullseye is hard on the plastic as well. All the high nitro content powders are.

    I put powder back in the original container after use. If you leave it in the hopper, cover it to keep it in the dark.
  17. Blue68f100

    Blue68f100 Member

    May 25, 2011
    Piney Woods of East Texas
    I left some powder in my dispenser over night one time and checked the dispensed weight when I continued in the morning. What I found was apparently it absorbed moisture over night and was throwing heaver loads. So now I return back to the original container when ever I stop.

    So run your own test and see what you run into.
  18. wingman

    wingman Member

    Dec 24, 2002
    yes---Return it to original "black" container after each use.
  19. Hondo 60
    • Contributing Member

    Hondo 60 Member

    Sep 6, 2009
    Manitowoc, WI
    I reload one or two boxes a day, so I usually leave powder in the dispenser.

    I have 2 dispensers & both are very dark, so it's not a good idea to do that.
    If I ever replace the cylinder tube, or buy another dispenser, I won't leave powder in em any more.
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