To the guys who are missing the Firearm Freedom Award: You don't have to collect every hidden Gun in the game like stated on some other post ( e.g find all 12 Shotguns etc..)
More likely you just have to use every gun, which means dont use it as melee but actually shot an enemy with it. And as well you don't just have to shot with it but finisht the lvl as well where you shot with it. Someone said earlier that you get the Achievement as soon as you fire but thats wrong.
I used Revolver, .45cal and Shotgun on Chapter 3 and finished it, used Rifle and Submachine-Gun on Chapter 10 and finished it again and by the time I picked up the Sawed off Shotgun on Chapter 5 I didnt got the achievement but as soon as I finished it, it popped up. So GL getting it
I don't need a reason, and I won't tell you why,
I'll just take you to hell by the edge of my scythe!