Hey, im now slinging for two months and im good with accuracy (60% at 50 meter) though bad at long distance, i use most of the time my 60cm long sling.
I got the idea from the acorn bread topic (I dont know, if someone already tried this, though I have read a lot of the forum); What if you grind the acorns and make dough (use only water, maybe oil if necessary) out of it. Then do not cook it, but just let it in a dry place, so that there wont get air in the dough. Then wait until its dry and its ready to sling!
You can make the dough in the perfect shape, or put any sharp thing in it for hunting. Its perfect for mass making and its not so dense that it is lethal to practice with, unless you put any metal in it
Because of the time of the year, I could not find good acorns, so I did an experiment with wheat flour. It is still drying so no results so far (I made a ball 3 minutes ago
). I will post pictures and my results asap.