Actually, the golf/slinging comparison brings to light several interesting dynamics possibilities.

I mean, look at how light that golf ball is.....and how slow, relatively speaking, the golf club is swung compared to a sling.

And yet the golf ball retains enough energy to fly up to 1200ft. or so.....the translation of a small portion of the club head's appreciable momentum, given it's mass, is largely responsible.  

Obviously, the magnus effect has borrowed some of the burden here.....for the golf ball would not travel nearly as far if spinning at the same rpm in spiral fashion.

Of course, the energy return signature of the ball is also critical, for how far would a ball of the same weight get if it were made of modelling clay?

All sorts of possibilities are opened up to the slinger regarding stored/elastic energy, and dynamic leverage scenarios....

Many years ago, after having witnessed slow motion footage of a club head's impact with a golf ball....I began to research the dynamics of aggregate mass momentum transfers.  After much consideration of how such may be employed to maximize a slinger's effective range.....I was somewhat dumbfounded at how little is apparently known about the dynamics of arcuate systems.  

The 'Golden Ratio' is found in a variety of geometrical expressions everywhere in nature and spiral forms comprise the tiniest observable particles all the way up to galaxies and beyond.

Even the title of our entire view of reality.....the 'Universe', in Latin simply means: "Single Curve".

Honor is given to the intrinsic spiral forms and their various expressions, constituent to the basis of all physical reality, by way of nebulous, pervasive references to them in the vernacular of many cultures.

The Latin uses several forms which mean: breath of life, breath, breathing, mind, spirit, courage, “soul”.

Just a few examples, for instance.....to receive an idea worthy of consideration is to be inspired. To end one's earthly life course, one 'expires'..... and shuffles off one's 'mortal coil.....

Every bit of mass in our reality is moving in spiral motion on a macro scale. All of it.  Such mass itself comprised of such motion even in the microcosm!



Once again, I wend my way into the philosophical.  




In summation, regarding the subject of adding distance...I would say that, considering the 'virtual weight' of our ammo as it nears release...I would think that one should be able to convert much of it to increased velocity while borrowing momentum from somewhere...

Liquidmetal, it's not just for golf clubs anymore.

TS

golf balls r pretty easy to aim.

This may have already been done. There are several slingstones in the Copenhagen museum that fit the description. They are football shaped stones with horizontal grooves cut into them.