Ammo Magazines are made with very thick walls, and a Thin Roof..
To direct the blast upward in case of catastrophic detonation..
That's the way they are made... Always have been!
Besides, ever see pics of the Bomb farms around Fields in Britain during WW2??
Stacks and Stacks and Stacks of them, under nothing but camo net!
Around any field, from any country, anywhere in a combat zone, for that matter!