Need some information about Mantinea 207 BCE

[D B Campbell]

...there's no mention of men, merely 'petroboloi'/stone throwers, which word appears to be the heart of the debate. Well, to clarify what you said, the lexica(LSJ et al) give petrobolos as "engine for throwing stones". It occurs some 16 times in Greek texts, where it almost always has that meaning ... Now in fairness, it can't have had that meaning before'stone-throwers' were invented ..., so its original meaning will have been a human 'stone thrower' [?!] ....but Polyaenus is a very late writer and is virtually certain to be using it in its 'modern' sense of 'stone-thrower' in the mechanical sense.... lol:

Lexica? You mention Liddell-Scott-Jones, which is always a good place to start. But it's not exhaustive. And it is fairly selective, taking its examples from a small core of texts.

In any event, you've made my case for me! You admit that the basic meaning of the word petrobolos is a man throwing a stone. Not an imaginary man. But a real man. Throwing a stone. Only the context would suggest otherwise to a Greek reader. So, Philon writing a book about catapults can clearly use petrobolos to mean "a stone-projecting catapult", without having to explain every time. Similarly, Athenaeus.

You also mention Polybius and Diodorus. Both interesting examples. Early on, Polybius uses the phrase petrobolika organa (literally "stone-throwing engine": 5.99.7), as if to make sure that his readers will know what he means by "stone-throwing". Diodorus does something similar at 24.1.2 (petrobolon organon). LSJ stick their necks out with Polyb. 5.4.6, where the meaning is only clear from the context. Polyb. 8.7.2 is another interesting one, where the reference to petroboloi kai katapeltai (literally "stone-throwers and catapults") again makes it clear that he means artillery.

So these examples that you have selected are not at all as clear-cut as you hoped. In two instances, it even looks as if Polybius and Diodorus go out of their way to explain -- "look, we're going to use this word petrobolos, but you must understand that it's actually a machine here, not a man."

Xenophon - before the invention of such machines), uses a derivative of this in reference to a stoning.

Xenophon -- a first-rate military author who lived before the advent of catapults -- uses the word petroboloi (not "a derivative" -- I don't know why you've used that odd term) to indicate what can only be men throwing rocks by hand. (Xen., Hellenica 2.4.12: "Behind the hoplites, however, were stationed peltasts and light javelin-men, and behind them the petroboloi.")

I never said there were no hand thrown missiles at all, and I meant 'lethal' in the sense of 'lethal' to an army ... But taking 'lethal to individuals', in your first instance the killing is shooting fish in a barrel by proper Athenian light troops - slingers and javelinmen, or maybe slingers alone - there is no mention of 'hand-thrown' ... both your examples are irrelevant.

Not shooting fish in a barrel, Paul. Not shooting anything, in fact.
Thucydides uses the verb kataleuô, "stoning to death". Anyone who has seen Life of Brian knows that this means throwing rocks by hand. It's nasty and it's lethal, even to hoplites.
(By the way, Thucydides says that it's the unarmoured psiloi who are given this task -- we don't know whether they're javelinmen or slingers, but that's not important because they have set aside their usual fighting style in order to beat the Corinthian hoplites to a pulp with rocks.)
Worse still, a phalanx has no reply to this kind of attack. They can stand and take it, or they can reverse! So I'm not sure why you think this is irrelevant to the discussion.

In this instance, immediately after this encounter, the Army's reaction was to refuse to take the field and Philip's reaction was to take an immediate interest in Artillery, become the foremost proponent of it in greek warfare, and even become the butt of jokes over his deep interest.

You certainly spin an entertaining yarn, Paul.
(1) How do we know that Philip's army immediately mutinied? It's not in Polyaenus. And we don't know the date of the encounter with Onomarchus. So where does this mutiny figure? (I have not memorised Diodorus ... yet.)
(2) How do we know that Philip's immediate reaction was to take an interest in artillery? It's not in Polyaenus. And we don't know .. etc. etc.