Any sling that tapers like a whip should be a pretty decent popper. The audio I posted was from a 4-strand cotton round braid with a large release knot and almost no fluff on the end. I guess the cm of loose cotton is enough, but I would like to make one that is designed to properly crack eventually.
@KTO I suspected you might be a practitioner of the disguised arts. I don’t normally give up all my secrets, but since we’re all friends here on the Internet, I will share my best disguise trick: changing socks. For example, in my lion hunting video, you may not have noticed that in some of the slow-mo shots, it was actually me prancing majestically in front of the camera, not my dog