Seeing as I was talking to Tint about this I thought it would be a good topic.

What is the grip and casting styles you use for each of the ammunition types:

Sphere, Foot ball/roman Gland/Almond shape and the acorn shape.

Then I thought we'd talk about the different physics on each shape of projectile.

For me I understand after reading allot and talking to Tint are as follows (These are my take on the subject).

Spherical shapes or close to that have  the magnus effect working on them at all times the rougher they are the more effect that will have and drag increase with each larger deformity from the spherical shape.

Foot ball, almond or roman gland shape uses the same theory the American foot ball-er uses to keep the ball from tumbling in the air by giving it a sideways spin. Thus point first.

The almond shape is an interesting one, seeing as they should by all account be like a dart and put themselves into a weight first position automatically.

This said and I welcome debate about the about detail.

What cast, grip and hand and arm movements would you think best serves each ammunition type and I you have the time how would you do it.

Allot of the details I have been thinking about come down to your wrist and hand action at release, but again I maybe wrong.

nightweave

i always use wide grip.
i try to use smooth stones, but i use rough ones when i run out of smooth river stones. 
i would love to take some water drop 1 to 3 oz lead sinkers over to a football feild and play with how far i can throw.
i use the underhand windup method with a sidearm release around my waist for distance, any at all.
i use something to the effect of the apache style for accuracy

Because Perth is a sand bucket I use tennis balls most of the time and any rock I can lay my hands on after that.
(Working on getting myself a load of size 6 sinkers to practice with)

Use a narrow grip which now is the same as what's on the wiki for a back spin requirement on the tennis balls.

When I get the sinkers will try to spin them, but don't exactly know how to do that yet.

Casting styles prefered are:

Figure 8 and Apache for everything and really long distance for me is underarm variant where you throw the projectile up in front of you.

  I also use an underhand windup releasing around my waist like Siguy.  When you consider ammo vs. casting style, all you really need to keep in mind are the length of your sling, the angle of release, the weight of your projectile and wind resistance. The only other variable is how hard(fast) you can swing the thing.  So if you suck at slinging and are casting a beautiful egg shaped piece of quartz, you might as well be a master casting a pop tart. In short you need both good ammo and a good technique or it's gonna be rough going. It really is a matter of balance & harmony.

Memorize a 440
                                  Jim

Nightweave,

When you are using a narrow grip, which cord is closer to your fingertip?  The release cord, or the retained cord?  If you have the retained cord closer to your fingertip, you will be more likely to put a top-spin on the rock.  If you have the release cord closer to your fingertip, you will be more likely to put a back-spin on the rock.  When I first tried a narrow grip, I held it the first way, with the retained cord closer to fingertip.  Reversing the grip, produced an immediate improvement in my slinging.

It is not just your style and your ammo, that interact with your grip.  It is also your sling.  A sling with a long pouch can be used with wide or narrow grips; a sling with a short pouch will lose its load when used with a wide grip.  I have a sling designed specifically for golf balls with a pouch 3.5 inches long (about three-quarters of a golf ball's circumference); with a a wide grip, the ball falls out somewhere during my swing.  I have another sling designed for anything; the pouch is seven inches long, and golf balls or small rocks just roll back and forth during my windup if I am using a wide grip.

I started with a wide grip (finger loop on ring finger), and the Greek styles as depicted by David Taylor.  I continued using wide grip when I was learning the Figure-8, but switched to narrow grip when I was learning the Apache style.  I tried the narrow grip with the Figure-8 when Nwmanitou showed us

how he holds a sling

and I found that it worked. This is also when I changed my grip so that the release cord was closer to my fingertip, as nwmanitou holds it.

I have less control of spin with a narrow grip, but it is not NO control.  With heavy or stiff cords and the Apache style, I can spin a rock any way I want (most of the time).  What I mean is, when it spins wrong, it is because I slung it wrong, not because the sling twisted in a way I could not anticipate.  Thn, flexible cords, on the other hand, are uncontrollable as far as spin goes: the rock spins however it spins.  Those slings I have to use with a wide grip, if I want any control.

Yesterday I was slinging acorns, and I was able to put a nice football spin on some of them.  Narrow grip, figure-8 and underhand styles.  Those I slung point first, I could see the cap all the way out; those I slung cap first, I could see the nut all the way out; those where I goofed and put a side-spin on it, I could see the whole acorn spinning like a top as it sliced off to the left.  The spin controlled the orientation, not the weight distribution.

I tend to favor a helicopter style, close grip, with my 84cm sling.  I have fair accuracy and power out to about 40 meters with that.  For range I use a hybrid helicopter/underhand that swings about 45° from vertical.  The only problem I have encountered with that, however, is that I manage to put quite a bit of top spin on my rocks with that style which works against its intended purpose.  Because of that problem I am trying to get comfortable with a powerful overhand cast that should reverse the spin and aid in distance.  Currently I can manage about 150-200 meters underhand with less than ideal stones, but accuracy is virtually nonexistant at those ranges.

I'm braiding/weaving a shorter sling (~40-45cm) now that I am going to experiment a bit with.  It seems that a shorter sling lends itself better (at least for me) to overhand and figure 8 casting styles.  With luck I'll increase both my range and accuracy once I can get a good consistent spin on my stones.

As for ammo, all that is available is irregularly shaped rocks.  There are a few of decent shape but the majority of nice rounded rocks near me tend to also be a bit flattened.  I have had virtually no luck in figuring out how to cast flat rocks.  Sometimes they spin, sometimes they tumble, sometimes I get a weird miscast.

Once the time and energy becomes available to me I plan on mixing up some mortar and making a few hundred good projectiles that I can get some good practice with.  While I do sling just about every day, the majority of my creative energy has been put into making slings themselves rather than acquiring good ammo.

I am a physics major with a keen interest in aerodynamics and fluid dynamics, so any experimental information you guys can give will be most welcome.

My sling is 80cm or so long, and my casting style is figure 8 for both short and long range. Sometimes I cast figure 8 sidearm or use apache or helicopter for accuracy. I often add a 360° spin to figure 8 because I find I can get more power that way, it doesn't hamper with my accuracy as much as one would think, and it looks like it's stolen from some cheesy movie.

As for ammo, all I really use currently are random rocks, which tend to make wild manoeuvres in the air due to their bumpy surfaces. I might get some rounder rocks or even make decent ammo one of these days, during the coming winter I'll probably be using snow/iceballs for slinging though. Ought to be a ton of fun even if the lightness might force the ammo to be huge. I'm expecting the results to be somewhat steadier than with rocks, but until I get my hands on some snow I can't really compare the two.