Stun round

Stun Rounds are used by the UNSC during training of new recruits. They are non-lethal, but they give the victim a feeling of what being in a war might be like and can cause injuries. The stun rounds have been used in training for both Spartan-II and Spartan-III trainees. Dr. Halsey once stated that Stun Rounds could be lethal at point-blank range when John was facing a heavily-armed guard in a Mk. 1 exoskeleton during a practice section in which Halsey watched them to make sure they were ready for the Project: MJOLNIR.