I've thought about running a lot of rocket boxes but decided against it as its a lot of weight per volume of storage. And their solution seems expensive and requires a platform and is more stuff to fail
That being said, you may try this idea out if you have an nrs frame, and want to devote a bay to ammo cans.
Adjust the crossbar spacing so the box just fits between the crossbars, but the handles wedge if you try and push it down. The box will be about half below the frame. Run a simple loop strap below the box and tension to support its weight.
Use a simple two piece loop strap with each end looped around the frame and handle and then over the box to lock it down. The loop strap when tightened will lock the handles tight to the frame, as well as tension the lower strap
To access the box, loosen the top strap but do not remove, just flip it to the side. Then open the box lid using the normal hinge method
Let me know if this works