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Left my carry and 1 clip in truck during that freeze your balls off weather. It’s commercial Ammo. Safe to trust or not? Brought it in house now. Not sure if that big of temp swing messes with the powder. Thanks

I leave ammo in the truck all year long ..........never had an issue and its been frozen several times over. Granted it's range ammo but never a hiccup

Will the ammo fire? Yes. I have never heard of any problems from -30 F to 120 F or more.

If you are asking if there will be some velocity changes when the ammo is fired at different temperatures? Yes, there will be some changes. Some powders are more sensitive to temperature changes than others. If a few percent differences in velocity is significant to you, then it should always be shot at the same temperature.

Not worried if velocity is a little less. Never really thought about it but this last 3 week spell really dropped and had me thinking. I reload so know about the sensitivity on certain powders. Just don't know what hornady uses in the 40S&W ammo. Thanks guys.

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.

There are some Marines from about 1950 who could probably tell you about ammo in the cold. I think they would likely state that the ammo is fine but make sure you work your Garand action once in awhile so it does not freeze shut.

Holland&Holland wrote:There are some Marines from about 1950 who could probably tell you about ammo in the cold. I think they would likely state that the ammo is fine but make sure you work your Garand action once in awhile so it does not freeze shut.

My late Uncle was there - talked about using frozen bodies from either side to make trench abutments as ground was too hard to dig.