Nice video and nice shooting Carbon, thanks!
I noticed just after you asked us to listen I think I heard a trumpet like sound that may have been air vibrating your lips as it escaped between one of your lips and the blowgun barrel at ~1:56
One advantage of a mouthpiece is to increase the seal between your lips and the blowgun as you shoot because the resulting pressure pushes your lips against the mouthpiece vs the tendency to push your lips away from the round barrel without a mouthpiece. Just an observation I made as I went from shooting with no mouthpiece to shooting with a mouthpiece.