Thanks for the feedback!
I actually tried to make it match w/ the beat; but I have got a feeling there are two problems:
1. I think sometimes the music starts a few miliseconds later than the game itself due to lag and this can shift the beat in relation to the shots
2. The music is 160BPM -- 1 beat is 0.375s and this is the timer I set for my shots. The game itself is 60fps -- 1 frame is 0.01667s. 0.375 is unfortunately not a multiple of 0.01667 so I think due to this the shots will start to go out of sync after a while. I think this could've worked better at 150BPM gameplay wise (1 beat is 0.4s and so I can use either 0.2s or 0.4s) but I haven't checked how the music sounds if I reduced the tempo to 150BPM. 180BPM can also work gameplay wise but from my experience my musics usually sounds silly at that tempo.