wow.  yeah i am always on the lookout for some new ammo possibilities

I tried the same idea, but in indoors. I was training some new styles and had a superball as a weight in my sling. Then the most terrible thing happened to me, the superball went airborn, it bounced around in my house and ended up in my forehead. Funny experience when I think it now, but I'm not going to do that again for sure.

Take the super balls and sling them either straight down a big empty street, or try to make it land on a parking lot, its fun to see em go so high, come down and bounce again.

when you were younger, did you ever take a super ball and hurl it at the ground right in front of you just to see how high you could get it to bounce?  i used to all the time (very carefully of course to not lose my balls  )

well not so long ago i decided to try the same thing, but with a sling.  i can tell you that on the preliminary throw, which was not very hard at all, using an overhand windup, the ball went higher than it could go if i threw it by hand, and then i lost it, so i never had the chance to try harder.

this is pretty fun to try, in addition to regular slinging with these.  i wonder what the limit would be...

I did that with the high bounce balls, glass marbles off  something hard like stone flags or concrete bounce even better.  One I played with a lot is shale, fairly useless ammo for serious slinging as it is so light and, often,  flat.  If you get the stuff from rivers it can be quite smooth though.  It's great for shooting at walls or cliffs.  If the range is fairly short it disintegrates in a puff of dust, which looks good, and leaves a small pointed cone behind.  You can draw the targets with it too.

I haven't tried this yet, just found it - solid wooden 1" balls or solid 3/4 " iron balls for $ 0.50 each from this trebuchet kit:


http://www.trebuchet.com/kit/tabletop/


Potentially lethal, so exercise caution!