How many rds of which load will you stockpile ?? Think . . . what size can,stacked how in can,will hold the most ammo.
Remember weight. A 30cal can stack properly will be heavy. Close to 40lbs. A 20mm can will be unliftable.
Buy when cheap. Stock it deep. If you don't shoot it,you can sell it or trade it. It will never be as cheap as it is today. --- SAWMAN