/*
        You can put this code where ever you want. Most likely you want it in the PlayerInteractEvent
        */

    Location location = player.getEyeLocation();
        BlockIterator blocksToAdd = new BlockIterator(location, 0D, 15);
        Location blockToAdd;
        while(blocksToAdd.hasNext()) {
                if (blockToAdd.getBlock().getType() != Material.AIR ||!shotprojectiledata.containsKey(projectile)) {
                    break;
        }
                blockToAdd = blocksToAdd.next().getLocation();
            player.getWorld().playEffect(blockToAdd, Effect.STEP_SOUND, Material.FIRE);
        }
        Snowball projectile = player.launchProjectile(Snowball.class);
    EntityData data = new EntityData(projectile.getLocation(), 15, 5D);
        shotprojectiledata.put(projectile, data);
        for (Player p : Bukkit.getOnlinePlayers()) {
            ((CraftPlayer)p).getHandle().playerConnection.sendPacket(new  PacketPlayOutEntityDestroy(((CraftSnowball) projectile).getHandle().getId()));
                    }

    //put this in whatever class you want or in it's own class
    public class EntityData {
        private Location firedfrom;
        private Integer range;
        private Double damage;
         public EntityData(Location loc, Integer range, Double damage) {
            this.firedfrom = loc;
            this.range = range;
            this.damage = damage;
        }
        public Location getFiredFrom() {
            return firedfrom;
        }
        public Integer getRange() {
            return range;
        }
        public Double getDamage() {
            return damage;
        }
    }

    //put where ever you want again
    public final static HashMap<Entity, EntityData> shotprojectiledata = new HashMap<Entity, EntityData>();


    @EventHandler
    public void onHit(EntityDamageByEntityEvent event) {
        if (event.getDamager() instanceof Snowball) {
            if (shotprojectiledata.containsKey(event.getDamager())) {
                EntityData eventdata = shotprojectiledata.get(event.getDamager());
                if (event.getEntity().getLocation().distance(eventdata.getFiredFrom())<=eventdata.getRange()) {
                    event.setDamage(eventdata.getDamage());
                    shotprojectiledata.remove(event.getDamager());
                }
            }
        }
    }