Historical accuracy of Celtic units?

[khelvan]

Is it not a bit of a problem to base a unit heavily on epic legends?

It would be, if we were. The stories of Cu Chullain are the only ones that you might be able to paint with that broad brush, and the evidence is compelling without them. So feel free to strike them from the list, if you wish.

On might ask why the Greeks don't get cart-sized stone throwing soldiers ala the Iliad.

Because we don't use legendary epics such as the Iliad as evidence for weapons, armor, or units.

Dun da nFerg was not a legendary epic, it was a work of history. No magic, legendary champions, or extravagance of any sort is found in it. It is surprisingly low key. It is a poem about an historical event; the Celts used such stories as a way to make the history easier to memorize. The poem mentions Gaul in the past tense, but states that the Britons still posed a threat, so it was post Gallic conquest, but before the southern Britons were conquered by the Romans.

The oral traditions of the Celts have resulted in three categories of works, if you will: Legendary epics, works of a religious nature, and serious histories. Of the three, only the serious histories can give us specific information about the Celtic military, for instance; the others are useful only for general information and for clues about Celtic culture, and perhaps corroboration of things found elsewhere.

While we cannot call the recorded oral histories 100% accurate, this does not invalidate them. Many things have been located as a direct result of the translation of these histories, or previous discoveries corroborating information found in them; burials, remains of objects and places, battle sites, and so on. Like any ancient work, the oral histories are evaluated on an individual basis as to their validity and accuracy.

We are careful to note which of the three 'categories' the information we use comes from, and are careful about the individual sources we use, noting which are more and which are less accurate. The stories of Cu Chullain would be less so, Dun da nFerg more so.

Is there any evidence of 2 handed hammers being used by Celts in any actual historic record or found in battle field excavations (in the Classical era)?

Dun da nFerg IS an actual historical record. Others exist, as well.

However, I have answered this above, though perhaps I was not precise enough. Chunks of all the weapons and armor noted in Dun da nFerg have been found in battlefield excavations, notably one east of Gort, south of Loughrea, near the Burren. Edit: Including parts of two-handed hammers and two-handed swords.