If I understand what you want, you want a Bullet that removes when it hits anything?

If yes, use:

function remove()
{
ptr_remove(me);
}

function bullet()
{
my.emask |= ENABLE_IMPACT;
my.event = remove;
while(1)
{
c_move(me, vector(13 * time_step, 0,0), nullvector, ACTIVATE_SHOOT);
wait(1);
}