Armor Penetration and Armor resistance.

[Thersites]

AFAIK tests performed by different people, from Napoleon III to modern scholars and reenactor groups consistently show that a heavy throwing javelin, such as a soliferreum or pilum will be effective, and armor-piercing capable at a range of 20 to 25 or even 30 m. Lighter javelins will be effective at the same range on unarmoured or lightly armoured targets, but seldom really armor-piercing capable. These same light javelins will still be useful at ranges over 40 m. and up to 60 m if thrown with the aid of an amentum and in salvoes or dense clouds, but their killing capacity will be very reduced. They can be useful for harassing and disordering enemy formations, wound horses and some men and generally 'soften' enemy formations. I am however a bit sceptical at the longer end of these ranges, as in real combat conditions all weapons tend to be normally used at the lower ranges, even nowadays.
Cheers