Pistol powders are generally of the fast-burning double-base type for use in short-barreled guns. Shotgun powders are also fast burning and double-base, designed to burn completely under low pressures. Rifle powders are generally slower burning to accelerate a rifle bullet down a long barrel with maximum velocity while producing minimum pressures.
Winchester has replaced metal powder cans with its new plastic packaging, which keeps volatiles in and moisture out of the powder inside.
As smokeless powders deteriorate, they generate small amounts of nitric acid. Stabilizers are added to these powders to absorb acid byproduct. Most powders have fifty or more years of life before the stabilizers are used up and nitric acid begins to leach out of the nitrocellulose, leaving plain cellulose and reducing the efficiency of the powder. Occasionally powder will deteriorate owing to acid residue that was not properly washed out in the manufacturing process. Such powder will take on an unpleasant acidic smell and a brown dust looking very like rust will appear in the powder.
Powder in this condition will not shoot well, giving poor ignition and low power. It should be disposed of. Metal cans containing powder will sometimes rust on the interior, producing a very similar-appearing dust, but without the characteristic odor. This does not harm the powder and can be removed by dumping the powder on a flat piece of bed sheet, spreading it evenly, and gently blowing off the dust.
The powder should then be placed in another container. An empty plastic powder bottle is good so long as it is clearly marked as to what it is. It is a good idea to mark containers of powder with the date of purchase and then use the oldest first. Opened containers of powder should be checked at least every year for signs of rust or deterioration if they are not being used. Sealed containers should be left sealed until they are to be used. Alcohols and occasionally camphor are added to stabilize burning characteristics. Powder containers should be kept tightly closed to keep these volatile additives from evaporating into the air.
Smokeless powder is toxic if ingested because the nitroglycerin component causes heart irregularity. British soldiers in WWI chewed smokeless powder from rifle cartridges to cause a brief though severe illness to get off the line, until medical authorities discovered this practice. Children have a tendency to taste things; smokeless powder should not be one of them.