I have an old Homak Gun cabinet that holds a ton of stuff but I only own a couple of long guns. the cabinet only has one weenie shelf on the top.

For years I've been stacking stuff on the bottom of the cabinet and it's long past time to build some sort of interior plywood shelving unit in order to maximize the space.

The shelving will have to bear quite a bit of weight (ammo, bulk bullets) and once inserted it will be set off to the right to allow the long guns to be stored next to it on the left. The two storage bins that snap into the inside of the door would probably be removed but I may design the shelf height to allow them to remain in place. Note that the unit has no "top" so that I may use a couple of plastic storage baskets to store stuff like holsters or AR mags.

1. Is 3/4" plywood overkill for this project?

2. The unit probably needs some sort of back piece to give it stability. Plywood? Or is Luan acceptable?

3. In addition to wood screws and wood glue what sort of braces (if any) would be used to attach the shelves to the side? I don't own any wood shop tools so using tongue-and-groove is likely not going to happen.

any help appreciated