no not even close - I presume you're talking about the crocodile.  
It's way simpler than that  
 
Project Crocodile
You take double walled pin pong ball halves (cut one in half and press smaller half inside larger - it works) These are the teeth.
Attach say six to a piece of wood and repeat. Two jaws.
Attach each jaw to a piece of wood and then fix the two arms together so that the jaws open and close like a pair of scissors.  
Also make sure you align the jaws so that the ping pong ball halves meet exactly.  
 
Then all you need is a bucket of cement and a sheet of plastic.  
Scoop up cement and close jaws to mould ping pong ball size cement balls. Tap jaws to loosen balls and turn out onto plastic sheet to dry.  
Repeat till you run out of cement.  
 
Now obviously there are a number of prctical considerations.  
Compression. At least one set of of teeth will need to have holes drilled in to allow compression of the cement into speheres.  
Also it might be necessary to spray the teeth with wd40 prior to the bite.  
 
Minor things and easily sorted.  
Can't see any reason why it won't work. Just haven't got round to putting it together yet  
Got lots of teeth lol  
Even got a jig for marking the exact centre of a half ping pong ball for the nail in point for attaching to the jaws.
Just not built it yet

i think i get it, nice idea

bump for anyone who's joined since 2009

I have some cement that I'm going to make projectiles from soon, but I think I going to use a melon baller to scoop out the spheres. I think it would be perfect for sling ammo production until the croc jaw is perfected. I also have an idea for a glans extruder with an irising nozzle to make biconicals, but no time to make it.
 
Edited:

just a quick addition.
 
I've changed my initial conclusion that 40mm is too big. Actually for target shooting the extra size and weight are perfect.  
 
The BPR is still under one of my workbenches.  
 
The ammo is probably exactly what we need for the hill fort project, so the BPR might be getting it's second usage fairly soon. I'm going to take a couple of the concrete balls with me tonight and see how they fly.  
 
I figure next time use a slightly stiffer cement mix with some pva added in and see how we go.    
 
Morphy:  sorry it's take me so long to answer you lol  
 
 
 
That's basically the same thing as project crocodile - I was just thinking make 6 at a time rather than one  
 
The other thing you could use would be a portioner (no I had no idea what that was either) or an Icecream scoop as I call it  
 
 
They'd be quick and easy to use, but you'd need a pretty stiff cement to get anything resembling a sphere.

Quote from curious_aardvark on Aug 28^th, 2012, 12:25pm:

 
Very nice...  Not sure how I missed this post when you posted in Aug.  I've spent the last couple days trying to work out a simple way of making something like this meat baller.  Apparently, someone already beat me to it.  This will give a slinger exact weight ammo every time.  
 
And I am currently working on experimenting with cement additives to get a stronger product and better consistency for making sling ammo.
 
Good find C_A.  

Quote from jlasud on Dec 7^th, 2012, 4:25pm:

 
I've tried icecream scoops, melon ballers, meatball makers and they were all more trouble than they were worth when making shot out of clay. I'd like to play around with it a little more but I am still faster at making them by hand. I have materials for a pill rolling tool but it's still a couple projects behind in the project que.

I've been using jlasud's cookie cutter method when cutting my clay into uniformally weighted pucks before forming by hand into biconical kinl fired stones.