Ok so you're saying instead of the rotations being horizontal, they are vertical and in the same plane as a figure 8 throw? I've slung like that before and it does work well. Although having tried it I find the figure 8 easier and you get the same results. Interesting theory but hard to prove.

Yes, David. Very much like your video.

A few details from the coin tipped me off on the vertical vs horizontal rotation. The first was the feet. On the coins both feet are pointing at the target. On several of the coins, the back foot is resting on the ball of the foot, like a sprinter waiting to start. This stance is very strong in direction of the throw. Image a sprinter on the starting block. You face him try to push him backwards. He's very strong in this plane and can easily resist. Push him from the side, and he'll go over easily. He is not set up to resist a lateral force.

Similarly, a slinger with their feet like this would be very strong front to back but very week side to side. He is ideally set up to generate power with a vertical rotation. He would not be able to generate as much power from a horizontal rotation.

The other clue was I noticed that some of the images the sling was not held perfectly horizontal but with the pocket slightly elevated. For a throw starting out horizontal, this would make for a non-ideal start. The payload and the applied force would be out of alignment. You would not get full tension on the cords from the start.

Having a slight elevation at the starting point, however, makes perfect sense if the initial rotation is in the vertical plane. The payload is perfectly aligned with the applied force. Exaggerating the elevation can also potentially add more power to the final throw.

One last thing I've tried to experiment with is power generation. I started with the sprinter's foot position. (back foot on the ball) From here I rocked back on the heel of the rear foot and ended with the throw with the back leg on the ball again. Minimal movement. My feet were in the same spot the whole time. I did notice a boost in distance.

Will keep playing with this. I've got to make some clay ammo next. Also, I've got some ideas on increasing rate of fire but want to experiment a bit more.

AM, how long was your sling and how heavy was your projectile?

Themistocles, I think you may be correct, also.

It's too bad they didn't have Youtube back then 

It's been my observation over the years that relying on non-military sources to accurately describe military tactics and procedures yields poor results. For example, an untrained non-slinger, witnessing a skilled slinger using a good fig-8 technique, will probably be unable to accurately describe the procedure. It happens so fast, it appears similar to an overhand throw, like a baseball pitch. They will be missing the crucial step, the rotation behind the head...
A second hand account, relayed by someone with a limited vocabulary to someone with enough education to write the procedure down, will probably miss even more detail.

Even modern-day military training manuals, complete with pictures and descriptions written for grunts can yield interesting and varied results when put into practice.

The pictures on the Greek coins, to me, look like they are standing in the ready position. A highly regimented military like the Greeks would have had a "by the numbers" system for teaching the sling. I would be surprised if they didn't use the fig-8, it makes the most sense if you have to train a bunch of slingers lined up in a long row.

I'm sure the commands were similar to modern rifle training…load, aim, fire.

I would love to have a time machine, just to see what they were really up to...

MH, you are very correct about interesting results from POG's reading and then trying infantry tactics.  Words were probably too small.  Or something. 

You have to keep in mind that some type of military training was mandatory for pretty much all the upper classes for the Greeks, while a lot of them wouldn't have used it, it would have been a weapon for someone below their station, they would have know how to use it and how to train and  slingers.

And I also think that you are correct about having a by-the-numbers way to throw.  They would have to know how to teach it to others and then use the quickly trained slingers in battle.  You could use a group of quickly trained townsmen with slings for defending the walls of a city, for example.

And you would teach them to throw in a style where massed slinging made up for lack of individual accuracy, sort of the Brown Bess of the Bronze Age.

"Would love to have a wayback machine as well. The fun of these speculations for me is that the the biomechanics of the human body are the same and we can test out theories. We will never know for sure what was done, but can we make good guesses based on what would work. For example, I think it highly unlikely that this starting position was used with an underhand cast.

Baseball pitching mechanics are an interesting analogy to slinging. I think the figure 8 is like a full windup pitch and the coin style is like a stretch pitch. In both cases, the latter part of the throw is identical. (Most of the power is generated here.) Also, the longer versions take more time but may generate slightly more power."

I definitely agree with the first point. Have you read Finney as well?  (If not, its a 2005 PhD thesis and he interpreted this position as the starting point of an underhand throw.) I know very little about biomechanics but it's definitely a promising avenue for future research.

As to the 2nd point, I really wish I had practiced with the figure-8 technique and could therefore compare it to the style we've been talking about. Referring to the two as a pitch from the windup and from the stretch seems very accurate, but so far I haven't seen a direct test. As the weather improves I can try to get proficient in figure-8, but its unlikely that I'll be running any more measured trials in the near future. If using the sling in a volley-fire tactic, (especially with less-trained users, like in the Brown Bess analogy) I think the simpler overhand style would be preferable to the figure-8.

The one from UNL is mine. Finney's paper actually isn't too bad, he just falls into the same traps that a lot of academics do when they are evaluating a thing that takes skill and practice to perform well. Unfortunately that makes the experimental component of the piece pretty un-usable, but he has lots of other discussion that is pretty interesting.

Figure 8 and half 8 sound pretty good. I've had problems communicating what the style was before, and this seems to cut through those issues.