This may have been revealed in another post but I just discovered a quick way to move shells from one gun or tank to another quickly, with your solider, grab the shell and drop them on the ground, they all are there, then take your soldier and pick them off the ground - he now picks up multiple shells at the same time - as many as he has room for in his inventory. I always hated the fact that you can't transfer all the shells with the move all button but with this trick no more dragging shells into the soldier one-by-one.