Is there something I am missing here? I see how the new primitive weapons work (damage cap) which makes sense and keeps most from being too deadly, while upping it a bit over DH levels. But what about primitive armor? Am I missing a rule about how they are handled? Or what makes them weaker than flak or mesh?

I'm pretty sure that Primitive Armour is handled the same way as any other armour, it's just that their AP is very low. The highest AP available for primitive armour is 3, and that armour weighs 28kg. From what I see, the rules doesn't state anything else.

Etaren said:

This - primitive armour is the same as any other type of armour now - they have no special rules.

That seems a bit odd, how a quilted vest is almost as good as light flak armor in the chest (minus the blast special rule for flak)

Well, it's not like flak armour is known for the flawless protection it offers.

Neither is a quilted sweater vest

I suspect the Quilted Vest armour is more alike a medieval gambeson, which was a lot thicker than a sweater.

Flak armour is basically the same sh*tty stuff they wore in the world wars, layers of thick cloth meant to stop ricocheting bullets and stray grenade fragments.

flak armour is roughly equivlent to the kevlar we wear in the forces now i think

I'm not sure about that, I'm pretty sure the description said it was just layers of cloth, although of course there are likely to be regional variants, not to mention the tabletop models and most art depict guardsmen with additional chest protection.

Kevlar is made from layers of cloth. Called kevlar, ironically

I stand corrected :-P

Edit: http://en.wikipedia.org/wiki/Flak_jacket looks like historically, the term has been used for a wide variety of body armour too.

Etaren said:

Like he pointed out, weight. Most primitive armour is heavy, and rather useless when compared to it's flak equivalent, as well as not getting the blast bonus

Flak armour is AP3, and one stage scarcer than quilted, while also being 3kg heavier. But for a full flak suit it is ap4, covers ALL areas and is 11kg for scarce, while the closest primitive has is a chain coat which covers head,arm and leg for 3 ap, is 28kg and average. Plus with the flak you won't stick out on Imperial, penal, chaos, hive, war, and most other worlds like Conan at a redemptionist gathering.

Also, primitive gets none of the nice upgrades (which are damned nice)