some dumb questions

[Sarcasm]

-what is the big metal 'piramid' on top of the Pilum? is it for extra weigth ->impact force?

I assume you're talking about the penetration tip. I belive it is quite obvious that it is a shape that allows it to better pierce armour (ringmail mainly) and wooden shields. The smaller the pressure point, behind a certain force, the better they pierce or cut. It's the same principle as a knife, or a needle.

But I believe that to be relatively empirical...

-wich factions will be stationed in Italy (4 roman? or else?)

Heh. You know better than that jerby...

-why does a Unit named Torikatai (=breastplate) argyraspidai hypaspistai wear a ringmail?

I believe the unit is called only Thorakitai Argyraspidai, and Thorakitai just implies that said soldier is armoured, not specifically with a breastplate. I think I have answered this particular question on another thread.

Forgot to answer the question about the swords. They are regular longswords I believe. It could just be the perspective.