Half of all the surplus IMR 4895 I purchased went bad.
The first 16 lbs, I used up eight pounds quickly. For whatever reason, I pulled the bullets on some of that stuff and found green corrosion on the bases of the bullets.
The last eight pounds, it sat around. When I opened the bottle top, it smelled bitter. Red dust flew around.
I gave it to a machine gunner guy. He put it in the laundry room. The bottle got a piece of laundry over it and over night acid gas from the bottle ate holes in the laundry. That freaked my friend and he poured the stuff out over the lawn.
Since then I have had surplus 4895 powder go bad in the case. Green corrosion on the bottom of the bullets and cracked case necks.
I was able to talk to a Navy Energics specialist. He explained that powder deteriorates from the day it leaves the factory. The Nitrocellulose and nitro glycerin want to combine to form a lower energy molecule. Nitric gas is released in the chemical reaction. The rate of combination is directly related to temperature. The higher the temperature the faster the reaction. Powder contains stabilizers. The Navy samples its powders and propellants. If the powder is outgassing nitric gas (as determined by a paper that changes color (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.
The Army does it different. The Army scraps small arms powders by clock time. Double based powders and ammunition are scrapped at 20 years, single based 45 years.
The military does not talk about this, but bunkers and ammunition storage areas have gone Kaboom due to old powder. That nitric acid builds up, creates heat, and the stuff blows up. It blows up inside the case or the shell.
http://www.liveleak.com/view?i=13c_1205681217
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.
If the powder has turned red, or smells like acid, it is way beyond its safe limits.
I talked to Alliant powders. They told me that if the plating inside the old cans is has rust spots, the powder is doing that, and the powder should be dumped.
I do not think it is wise to mix old powders with new. Why have the whole lot go bad?
Per the expert, the best storage conditions for powder is artic cold. That is cold and dry. He said water exposure damages powder.
Primers, the expert said the shelf life is like forever. I think cool dry would be be good for them.
I thought this was interesting, maybe someone else will:
http://www.almc.army.mil/alog/issues...t_stab_eq.html