The round on the left has never been chambered. The round on the right has been repeatedly chambered and the bullet is set back in the case.

How Long Does Ammo Last?

How long does ammunition last? We get this question fairly often with a new firearm purchase. A customer will buy a box or two of quality defensive ammunition and wants to be sure that the ammo will work on demand.

Most ammunition stored under cool, dry conditions will remain good indefinitely. That’s the short answer.

Ammo stored in a garage in Florida (for example) will be exposed to higher humidity and a greater range of temperature. This may shorten the life of the cartridge, which is still likely to last for many years. Let’s look at the individual components that make up a round of ammo. They are the case, primer, gunpowder, and bullet.

  • Cases are usually made of brass, whether raw or nickel plated, and sometimes aluminum or steel. Neither brass nor aluminum will be affected by age. Steel has the potential to rust but most steel cases are polymer coated for moisture protection.
  • Bullets likewise are mostly copper and/or lead, and neither of these will be significantly affected by storage.
  • Gunpowder can be damaged by exposure to moisture. Most of the time, the bullet adequately seals the mouth of the case from even temporary immersion in water.
  • Primers can also be damaged by exposure to moisture. However, the primer fits tightly into the case, which usually seals it against moisture or even brief dunks in water. Additionally you will often find a colored ‘primer sealant’ that manufacturers may use to further protect against moisture intrusion.

Carry Ammo

If you carry a gun, it’s prudent to practice regularly (minimum once a month). Most people will carry one type of ammo and practice with another due to cost. However, repeatedly chambering the same round can cause dangerous pressure spikes as the bullet is pushed into the case. (Carrying without a round in the chamber is not a valid option.)

Rechambering ammo can be a problem. The round on the left has never been chambered. The round on the right has been repeatedly chambered and the bullet is set back in the case.
Rechambering ammo can be a problem. The round on the left has never been chambered. The round on the right has been repeatedly chambered and the bullet is set back in the case.

Each time you unload and clear your carry pistol, pay attention to the round that was in the chamber. If the round is pushed further back into the case than a fresh round from the box, it should not be reused. One solution is to set aside any round you remove from the chamber, and collect all such rounds for later practice. This also gives you the benefit of practicing with your carry ammo.

As with ammunition stored in your garage, ammo that you carry will be constantly exposed to changes in temperature and humidity (going in and out of heated/air conditioned spaces, left in a car for brief periods, etc.) While this ammo will maintain it’s mechanical reliability for long terms, we recommend the practice of shooting and then reloading your gun using fresh ammo at least annually.

Informal Testing

One of our managers dug up a handful of old pistol ammo, including 10 rounds of 9mm Winchester Black Talon. This round has not been on the market since around 1993. This ammunition is almost certainly more than 20 years old. It had been carried at one point, so it probably saw at least a few months of Florida climate swings. We fired it on the range without event.

Black Talon 9mm. To look at it, you wouldn’t think this ammo is two decades old.
Black Talon 9mm: To look at it, you wouldn’t think this ammo is two decades old.

In conclusion, ammo isn’t all that perishable. Store it cool and dry, and rotate your carry ammo regularly. Don’t repeatedly chamber the same round, and you’ll probably be fine.