Shuriken collision detection is sparse

I'm having trouble with my particle collisions. They seem to happen much less frequently than it would seem they should. In this picture, the system has an emission rate of 100 and has been emitting for a few seconds already, but the collision detection has only registered three hits.

Here's my code for the particle system:

 using UnityEngine;
 using System.Collections;
 
 public class SprayGun : MonoBehaviour {
 
     public float freezeDecrement = 10.0f;
     private ParticleSystem prtSys;
     private CharacterInput scriptCharInput;
 
 
     void Start()
     {
         prtSys = GetComponent<ParticleSystem>();
         scriptCharInput = GameObject.Find("Character").GetComponent<CharacterInput>();
     }
 
     void OnParticleCollision(GameObject other)
     {
         ParticleSystem.CollisionEvent[] colEvents = new ParticleSystem.CollisionEvent[prtSys.safeCollisionEventSize];
 
         int numCollisionEvents = prtSys.GetCollisionEvents(other, colEvents);
         for (int i = 0; i < numCollisionEvents; i++)
         {
             if (colEvents[i].collider.name == "Character")
             {
                 scriptCharInput.xTransferEnergy -= freezeDecrement * Time.deltaTime;
                 print("BOOM");
             }
         }
     }
 }

Any ideas? Does it have anything to do with using World (currently selected) vs Plane collision? I couldn't find any good documentation explaining the difference.