having a aiming bug with my one tower

Unity Engine
1

I am making a tower defence game and one of my towers are having a problem where it aims off to the side, I think it is something with it needs to be in 0,0,0 couse then it can find its target fine.
Here is my code:

using UnityEngine;
using System.Collections;
using System.Collections.Generic; 
public class Ground_Turret : MonoBehaviour {


public GameObject myProjectile;
public float reloadTime = 1f;
public float turnSpeed = 5f;
public float firePauseTime = .25f;

public float errorAmount = .001f;
public Transform myTarget;
public Transform[] muzzlePositions;
public Transform turretBall;

private float nextFireTime;
private float nextMoveTime;
private Quaternion desiredRotation;
private float aimError;


public List<Transform> enemiesTarget = new List<Transform>();
void  Start (){

}

void  Update (){
	
	
	if(myTarget)
	{
		if(Time.time >= nextMoveTime)
		{
			CalculateAimPosition(myTarget.position);
			turretBall.rotation = Quaternion.Lerp(turretBall.rotation, desiredRotation, Time.deltaTime*turnSpeed);
		}
		
		if(Time.time >= nextFireTime)
		{
			FireProjectile();
		}
	}
}


void  OnTriggerEnter ( Collider other  ){
	if(other.gameObject.tag == "Ground Enemy")
	{
		enemiesTarget.Add(other.gameObject.transform);	
		nextFireTime = Time.time+(reloadTime*.5f);
		myTarget = enemiesTarget[0];
	}
}
	
void  OnTriggerExit ( Collider other  ){
	if(other.gameObject.transform == myTarget)
	{
		enemiesTarget.Remove(other.gameObject.transform);
		myTarget = null;	
	}
}


void  CalculateAimPosition ( Vector3 targetPos  ){	
	Vector3 aimPoint=new Vector3(targetPos.x+aimError, targetPos.y+aimError+1700
			, targetPos.z+aimError);
	desiredRotation = Quaternion.LookRotation(aimPoint);
}

void  CalculateAimError (){
	aimError = Random.Range(-errorAmount, errorAmount);	
}


void  FireProjectile (){
	nextFireTime = Time.time+reloadTime;
	nextMoveTime = Time.time+firePauseTime;	
	CalculateAimError();
	
	
	foreach(Transform theMuzzlePos in muzzlePositions)
        {
            Instantiate(myProjectile, theMuzzlePos.position, theMuzzlePos.rotation);
        }
	}
}
2

You are using .lerp to change your rotation. try the method RotateTowards http://docs.unity3d.com/Documentation/ScriptReference/Quaternion.RotateTowards.html

I would also try commenting out your AimError till it starts aiming perfectly first.

3

How would you put that function in i have played a little round with it but i can only make it aim straight forward, should mention i need to add +1700 to the targetPos.y in aimPoint or else it goes comeplete bonkers.