Depends on how tall you are...
M203 or 40mm rounds have safe arming distance where the projectile
must travel (and spin) a certain distance (remember somthing like
15m for HEDP) before it is armed. This is cleverly done by having
an internal weighted disk which needs to be rotated a fixed number
of rovolutions before fuze is 'live'.
if you misfire when weapon pointed downwards, the round will embed
itself (near your frigging foot?) but what happens next is anyone's
guess. Most likely become a 'blind', more likely become a
rebounding projectile (hitting some poor fool) and may arm itself
but not explode. never tried don't care to guess.
M203 is single shot weapon, although AGL is designed to work
like whar-lan gren launcher.
By the way:
is not gren launcher, its an (?)arwen smoke grenade projector to
fire tear gas cannisters at rioters. used in Singapore Police
Tacital Reserve Units ("ang chia")