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.

"Proper paper" in the context of slinging.org likely refers to: VID-20220418-WA0011mp4

Using tightly rolled paper or improvised paper materials for ammo. I cannot play the video to confirm, but

Specific types of paper or cardboard used for making targets. VID-20220418-WA0011mp4