I discovered something strange today.  I'd made a new sling in the hope of some iron ball bearing which we can sometimes get from the cement works.  It had a small pocket designed for heavy 3/4 to 1 inch spheres.  As it happend we didn't get them as they wern't changing them yet.  However took the sling anyway to test.  Where we sling there are few rocks so we collect them on the way.  I collected a lot of small for the sake of the new sling.
 
When we got there it was very windy and gusting.  A sling held out dangling was blown to between 45 degrees and flat out, the gusts meant that it was also very erratic and changed from second to second.  The rocks were way too light for that, they still fly ok but the casts were definately affected.  The first shot, during a lull,  was a good hit which pleased me as my new sling has broken its duck but after that rubbish.  So I switched to a differant sling, bit of a sail for a pocket in those conditions but could take bigger heavier ammo.  Slung the heavy stuff out and had the light stuff left.  Didn't want to use the new one as it also has a big tassle.  So I played with slinging styles, under, over, side no good.  Tried adding windups and that helped but still not sharp and it felt like trying to put a lot of vim into such a light thing was messing up my arm.

So I tried the figure of eight, which is not one I am confident with yet, and it felt a bit dangerous.  So just to remind myself what I was doing I did the throw shape several times very small only using wrist, arm nearly straight out in front,  apart from a big start to get it out to the side.   It hit, quite hard.so did the next one.  I stuck with the techique and, apart from a couple, got hits and very near misses.  These stones were too small for the sling and yet wow did they go.

It's not logical but it seems that in high erratic wind, with stones too small for the pocket then a good techique is to use a crippled figure of eight, big start then just twirl the sling on the end of a nearly  outstreched arm, several windups to get maximum speed and let fly with hardly anything from the upper arm, a tiny bit from the forearm and a wrist action a bit like a dart thrower to cast.  Shouldn't work at all but it did for me this afternoon.

Yes sort of, that was the side arm I was doing with the bigger rocks.  I think I've worked out what was going on.  Leverage was working against me.  The extended moves which are generally better are more affected by the unpredictable wind so wern't coming off at all well.  Adding a wrist twirled wind up first helped a bit as it got the speed up while the lever was short.  My overheads are mostly extended throughout so worked least well.  My usual underhand is the same and wasn't so good either.  I also have a mostly wrist twirled windup for one underhand style which extends during the final cast, it feels like flicking it off the hip which is what I call it, quite good for keeping energy in the sling for a while and then choosing a target at the last moment.  That worked best of the usuall shots.  A partial helecopter, only using a wrist twirl for wind up and a bit of elbow for the cast, wasn't utterly dreadful either. 

All the wrist twirled windups on the above shots were in the same plane so cumulative errors came in due to the wind.  They were all just good enough to lead into an extended cast for the heavy stones but no way for the light ones.  Not good as casts in themselves either.  I think using a figure eight shape wrist twirl helped to average the errors out and because I didn't extend for the cast the wind couldn't get the leverage to change it much at the end.

Might have been that.  In calm conditions extended is definately better.  Even so,  suprising power for a shot which is essentially wrist twirl and precious little else.