Yes and no, I used to sling when reenacting ancient Greek soldiery, but recently I'm having not so much opportunity to practice due to different reasons. I'm however busy since 25 years with ballistics of modern and ancient weapons and the abilities of the sling had interested me for long, partly because I like the simple and ingenious principle of the weapon and partly because there are so many under- and overestimations of sling performance in literature and on the Internet.