If you can tell me is in the video or what material they are using, I can give you more specific information on that technique. Directory /forum/yabbfiles/Attachments - Slinging,org
Using tightly rolled paper or improvised paper materials for ammo. VID-20220418-WA0011mp4
I cannot play the video to confirm, but I suggest checking the slinging.org forum for the thread matching that attachment name for the exact context, as attachments there often depict experiments with different materials. If you can tell me is in the