Robot turrets move and fire

It sounds like you simply need to either raise the position of the bullet's starting position, or - if your turrets are a separate gameObject, use the turret's position instead of the legs. (Presumably your script is on the "legs" gameobject, and the rotating turret is a child object of the legs?...).

Eg - Instead of:

var bullet = Instantiate( bulletPrefab, transform.position, turret.rotation);

You could either have:

var bullet = Instantiate( bulletPrefab, turret.position, turret.rotation);

Or:

// bullets start 2 units higher:
var bulletPos = transform.position + Vector3.up * 2; 
var bullet = Instantiate( bulletPrefab, bulletPos, turret.rotation);