Simple question: I have armor. I want to make it Hardened (like Milspec). What (in addition to ranks in Armorer) should I need to pull that off?
If I am understanding you, you want to self make a suit of hardened armor using skills??!?
OK.
First, you need some engineering skills to design the suit in an extended test (probably a test around 20 hits or so)
Next, you need some knowledge skills for materials that would be suitable to your purpose.
Finally you need a crafting skill (like Armorer) to actually craft the suit in an extended test - again probably 20 hits or so.
You also need a Facility to do this type of work.
*****
Now, just so you understand what hardened armor is: Hardened Armor is generally a material so dense or thick that it completely absorbs the full kinetic impact of the projectile so that none of it is transferred to the wearer.
When talking about flying lead, you are talking about a LOT of energy! For example, a .44 mag 300 grain round hits with 1411 Joules of energy. - and that is not the top end, just what I shoot! that 1400 joules is similar to the impact energy of most assault weapons as well (the standard 5.56mm hits with 1398 Joules).
and in case you are wondering, 1400 joules = roughly 1000 foot pounds of pressure...
So you need to design a suit that can shield you from a Ton (literally!) of force and not that that impact work against you...
Good luck.