Magazine and Powder store

Magazine noun - A storehouse (as a compartment on a warship) where weapons and ammunition are stored.

Powder store is a synonym for magazine. In some cases you can use "Powder store" instead a noun "Magazine".

Powder store noun - A storehouse (as a compartment on a warship) where weapons and ammunition are stored.

Magazine is a synonym for powder store. You can use "Magazine" instead a noun phrase "Powder store".