Shotgun slugs aren't really in need of an upgrade, and considering there are so many different types of rounds available it seems more constructive to improve existing ammo rather than creating anything new.
But YouTuber TAOFLEDERMAUS isn't making videos for the sake of progress- they're just having a blast making shotgun ammo out of whatever their viewer's suggest, like Silly Putty.
Silly Putty may not work as an effective shotgun shell filling, but these glass slugs made by Subconscious Design are terrifyingly effective!
-Via Boing Boing