since9 wrote:
I've fired 40-year-old ammo (properly stored) with the same reliability as that I bought off the shelf yesterday. The quality wasn't as good, but the manufacturing techniques back then weren't either.
"BACK THEN" .. What do you mean "Back Then"? There are a lot of people here who do not consider 1970 as being "Back Then". To some of us 1970 might be reasonably called "When" but 40 years is not ALL that long ago for many of us. :lol:
Nothing much has changed in manufacturing of ammo in the last 80-100 years that would effect storage qualities. The introduction of nitro cellulose based powders fixed a lot of problems. There have been improvements in the speed of the machinery, and developments in bullet design, a few new powders have been developed, and certainly new calibers have been introduced. But the basic elements of how ammunition components are factory assembled has not changed much since at least 1900. There have been some advances in scaling down commercial loading concepts for application by re-loaders but that is about it.
There are only two major concerns with long term storage, Stabilization of the storage environment for primers and powders and protection of the ammo from any mechanical damage or corrosion. Unless you plan on storing your ammo in an acid bath or under water, the casings and bullets themselves are relatively impervious to aging. However some older powders are sensitive to temperature over time as are some primers. In fact some of the older powders contain volatiles that may be forced into vapor under high heat conditions.
Exposure to wide ranges in temperatures, vapors of all kinds, direct contact with oil and mechanical damage from routine handling is why ammo used for carry should be swapped out from time to time. How often is a personal decision based in large part of how much you value your own life. In my case when the ballon goes up I do not want to wonder if the weapon will go bang when I pull the trigger. SO I swap out my ammo often. YMMV.
Most modern smokeless powders are not really destroyed by water. You can actually drench them, dry them out, and they will still burn. Some powders will expand when wet and this can cause changes in internal pressures if the ammo is ever fired, up to and including blowing the gun up. Some of that pressure is the result of the water itself turning to steam. The contact sensitive explosive used in primers are not as good at tolerating water. But they have the additional protection of being sealed inside their own little protective capsule under the primer anvil.
If either of flammable components comes in direct contact with oils the game is usually over. But since both of these components are more or less protected inside the cartridge, storage techniques must be designed to defend against the entry of water, oil, or vapors of any kind through the area around the bullet crimp and the primer pocket. Both of these are typically sealed only by a tight fit of the components and they can "leak".
Most ammo made under military and some LEO contracts will have a sealant applied to the primer area to prevent entry of damaging liquids and vapors, or any possible loss of volatiles from the powder. In some cases civilian ammo will also be made with sealed primers. The bullet crimp area is another matter. There are almost never any sealants applied to the bullets as that would cause wide variations in pressures between each round crippling any reasonable expectations for accuracy. In some cases lubricants used in the bullet insertion process can provide some additional protection against leaking around the bullet.
So here is the deal. Your storage system must be designed to protect the primer pocket and the bullet crimp from intrusive attack by liquids and vapors. In addition you must protect against mechanical damage (crushing, denting, direct corrosion, etc). The best way to do this is to assure that the ammo is in good condition at the start, placed in a STURDY vapor locked container with a desiccant to absorb harmful vapors inside the container. The cheapest and easiest way to get all of that in one package in the surplus military ammo can. If you want to add a plastic wrap inside the can have at it, but the storage technology of the military ammo can is time tested and proven.
Buy it cheap & stack it deep.
