You can use Raycasting. Your bulletPrefab should have a script that tests if it hits something (this requires the objects you want to hit, to have a collider).

The bullet script could look like this:

#pragma strict

// The position in the previous frame 
private var previousPosition: Vector3;

function Start () {
	previousPosition = transform.position;
}

function Update () {
	Fly();
	HitTest();
}

function Fly()
{
 	//... moves the bullet ...
}

function HitTest()
{
	var forwardDirection = transform.forward;
	var raycastDistance : float = Vector3.Distance(transform.position, previousPosition);
	var raycastHitInfo : RaycastHit;
	// Makes a raycast that returns true if it hits any colliders. 
    if (Physics.Raycast (previousPosition, forwardDirection, raycastHitInfo, raycastDistance)) {
    	// -- Hitted a collider --
    	OnBulletHit(raycastHitInfo);
    }
    previousPosition = transform.position;
}

function OnBulletHit(raycastHitInfo : RaycastHit)
{
	var hitObject : GameObject = raycastHitInfo.transform.gameObject;
    Debug.Log("Hitted: "+hitObject +" at point: "+raycastHitInfo.point);
    // ((AIScript) hitObject.GetComponent("AIScript")).OnBulletHit();
    Destroy (gameObject);
}

Yes, if you are using raycasting, you can save the points (Vector3). Which afterward you can use for anything you would like. I wouldn't save all of the points, for as you said, it will decrease the FPS and performance, however, you can use just one variable for a point and use it to "capture" each of the shots.