is there a way to do this offline? or do you really need a coop player? and can you give some info about save game? when the other player quits and rejoins does he always use the same save? and if player A has already 5 mags could he drop all five and player B can pick them all up and then player A quits and reloads save+joins with his 5 mag save and can let all of them drop again?
this is a great glitch. only problem: it probably can only be done online so if capcom decides to patch it it's no longer possible.