The following story best illustrates this tip: A long-time client's safe was subjected to an intense home fire. The fire burned for hours at very high temperatures. Despite this onslaught, paper contents within the Brown Gun Safe were kept below flashpoint. The multiple cases of .50 caliber ammunition at the base of the safe, however, did ignite. When fired through a gun, bullets produce very little smoke. When ignited through non-standard means, however, excessive smoke is a common byproduct. In this instance, the erupting ammo cases obliterated all contents within one foot of the ammo cases and caused heavy smoke damage to the rest of the safe's contents. Even with the extensive smoke, most of the safe's contents, largely paper memorabilia and photo albums, survived intact. Had there been no ammo containers, however, all of the safe's contents would have made it.
Think twice before storing any ammo in a safe, as your exposing the other safe contents to higher risk.
Avoid storing large amounts of ammo or powder inside a safe. If ignited, the ensuing pressures can outpace the safe's ability to safely vent, creating the potential for a safe grenade.