How would you go about playing firing sounds?

Hey guys,
I am working on a third person shooter and we have some lag issues when it comes to automatic guns.
We believe the issue might be due to the way we currently handle the firing sounds;
We have about 15 gun sounds (single shot) that we iterate through them so the sound isn’t too repetitive, but it seems to cause lag when you play so many sounds at once (500RPM)
And its especially noticeable when there multiple people using machine guns (our game has servers that allows up to 50 people)
The issue only surfaced when we fixed a previous firerate issue that caused weapons to fire very slowly -
We tried to disable bullet trails / effects / the actual raycast and came to the conclusion that sounds were causing the issue

Does anyone know whats the best / most efficient way to handle sounds?