The third person animation of the AR2 (Pulse Rifle) implies the removal of the magazine, even though the magazine never leaves the gun. The first person animations, however, shows an internal loading mechanism, where each pellet is 30 rounds.
The ammunition for the MP7 submachine gun is shown to have an icon of rifle ammunition and uses different ammunition than the pistol. The MP7 in reality fires the same 9mm ammunition as the pistol.
Valves sometimes turn to the left to close, when the international standard is to turn to the right to close.
The MP7, referred to as just the SMG in game, has a secondary fire grenade launcher. The MP7 has no grenade launcher attachment, and there is no room for it to be launched otherwise.
The SPAS-12 Shotgun has a secondary fire that allows two shells to be fired at once. There is no second barrel for another shell to fire, and the SPAS-12 does not have this function.
The grip/magazine on the MP7 is too far back to allow for movement of the bolt as on a regular MP7.
The drums marked 'Flammable' are explosive and not flammable.
At one point, the Player, Mr. Calhoun, and a few others are trapped when the doors are closed. In spite of the doors being shut normally, they are cut open as if they had been welded shut.
Weapons sometimes reload themselves if unequipped.
The printer in Dr. Kleiner's laboratory is printing so fast that it should quickly jam because the receptacle is filling so quickly.
The maximum ammunition for each weapon should be a multiple of the maximum ammunition that can be carried in a magazine for that weapon.