Good idea but keep looking. Jobox and Knaak and others all make cabinets that would work better that a chest. The cabinets are just as strong and secure as the chest.

Be careful with shelf material. Wood will hold moisture and rust out ammo cans. It's not much problem around here with the low humidity but some places it can cause problems in a short time. Concrete is porous and passes moisture that can cause rust also.