Just to add a point - the "volley" part of course indicates that the intention was that an entire section of infantrymen would be doing this long range firing simultaneously - and certainly not at a man-size target, but rather at an entire enemy unit or emplacement. The high angle of fire would result in multiple descending projectiles into "beaten zone", which might inflict casualties, but would certainly serve to at least disrupt enemy activity in that impact area! 
