This is a model I made for me and some friends to test how well filament protects against airsoft. Results were conclusive: It does okay.

With 3 walls, 15% grid infill, and 100 mm/s, this plate does well with PLA, but PETG or ABS would be safer. The plate can withstand many shots from an airsoft rifle shooting 300 ft/s on average. 

DO NOT USE FOR PROTECTION AGAINST METAL BB WEAPONS.