Bullet Spread axis compression

Hi there! I'm trying to implement some random bullet spread (for a shotgun effect). I've noticed both my implementations have the same unexpected issue. When firing along the world z axis, the spread appears as expected, as below:

However, when firing along the x axis, the x axis spread of the shotgun appears to compress towards 0, like below.

This is the method I'm currently using, where I'm implementing the spread value per "pellet" cast.

 void FireScatter(){
         
         //one round should give multi pellets
         roundsInMagazine--;
         nextFire = Time.time + rateOfFire;
         
         float rad = 0.0f;
         float spreadX = 0.0f;
         float spreadY = 0.0f;
         //fire a ray for every pellet, with each one getting random spread
         for (int i = 0; i<numShotPellets; i++) {
             
             rad = Random.Range(0.0f, 360.0f) * Mathf.Rad2Deg;
             spreadX = Random.Range(0.0f, spreadFactorX / 2.0f)* Mathf.Cos(rad);
             spreadY = Random.Range(0.0f, spreadFactorY / 2.0f)* Mathf.Sin(rad);
             Vector3 deviation = new Vector3(spreadX, spreadY, 0.0f);
             
             Vector3 direction = cam.transform.forward;
             
             Ray ray = new Ray(cam.transform.position, direction + deviation );
             
             RaycastHit hit;
             if (Physics.Raycast(ray, out hit, range, mask)){
                 if (hitEffect)
                 {
                     Instantiate(hitEffect, hit.point, Quaternion.FromToRotation(Vector3.up, hit.normal));
                 }
                 else
                 {
                     Debug.Log("No hit effect assigned");
                 }
             }
         }
     }

Could someone point out to me what the error is in the logic here that causes this issue? Just having a little trouble with it myself. Thank you in advance!