by crbutler on Fri Jan 12, 2018 12:19 am
The issue with cold and ammo is that the powder is not as energetic while cold if it is a temperature sensitive powder. You lose a little to some velocity if you fire it while it's cold.
As long as the case is sealed, cold won't cause long term degradation of the ammo in and of itself. A poorly sealed case can allow humidity in, which will cause issues if you repeatedly do so over time, but just leaving the ammo out and then warming it before you shoot it, no problem unless you leave it out for years. Heat causes more issues than cold, and even then it's good for years if sealed in a case. How many years, who knows...that's why they recommend changing out your carry ammo annually, amongst other reasons.