1. Go to Agia Marina (example), choose a house with blue windows
2. place a soldier behind one of the blue windows
3. place the player on the other side
4. shoot the soldier through the window e.g. with a 9mm sidearm or PDW (Sting in my case)
Observed:
Only assault rifles can successfully penetrate these really poor windows; some shots of the lower velocity gun seem to penetrate but slow down too much or change flight path too heavily.
Expected:
Any gun in the game should be able to penetrate and hit a target behind such a window.