Andy Griffith
Member
I've heard that the only things that will change the properties of modern smokeless powder is high heat over a long period of time and moisture.
Moisture can rarely enter into the inside of a factory sealed cartridge- even those stored in a humid basement for 50+ years will likely be just fine. Unless of course, they happen to be paper shotgun shells.
Heat isn't the normal kind- even being out in an attached garage likely won't change it or even in your car during a hot summer, but if you find cartridges out in a wreck of a car that has been sitting in Death Valley for a time, I probably wouldn't shoot them, as smokeless powder exposed to high heat (150F+?) gets more powerful and unstable over time.
Moisture can rarely enter into the inside of a factory sealed cartridge- even those stored in a humid basement for 50+ years will likely be just fine. Unless of course, they happen to be paper shotgun shells.

Heat isn't the normal kind- even being out in an attached garage likely won't change it or even in your car during a hot summer, but if you find cartridges out in a wreck of a car that has been sitting in Death Valley for a time, I probably wouldn't shoot them, as smokeless powder exposed to high heat (150F+?) gets more powerful and unstable over time.