@Override
  public void onUpdate() {
    super.onUpdate();

    if (!this.worldObj.isRemote) {
      this.dataWatcher.updateObject(18, Math.max(0, this.getRightBarrelOffset() - 1));
      this.dataWatcher.updateObject(19, Math.max(0, this.getLeftBarrelOffset() - 1));
    }
  }