Humidity and varying temperature extremes are the enemy of ammo. If the safe is not in a stable environment you will want to make sure you have a way to dehumidify the air inside. For a small lock box or safe, a Goldenrod dehumidifier will work. I've always wanted to make a gun cabinet like this
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Joe
See Porsche run. Run, Porsche, Run:
`87 911 Carrera