Weapons and ammunition are stored in an armory, magazine, silo, arsenal or at a weapons or ammo dump. In a home they should be stored in a secure safe or chamber/trigger locked with ammunition locked up separately.
An arsenal, a weapons cache, etc. Armoury
Weapons are kept in Armouries. Ammunition is kept in a magazine. They should not, never ever, be stored together.
Arsenal or armory.
Arsenal
An army's guns are generally stored in an armory. These areas are often heavily guarded. They can hold guns, ammunition, and other weapons.
armoury
a weapon cache
An armoury is a place where weapons are kept (stored).
Stored in moderate temperatures and low humidity, ammunition can be stored for decades.
Explosive room
weapons are stored in a tariif
Armoury, magazine, or silo. Probably others also.