High explosive ammunition

High Explosive Ammunition is a type of ammunition used by the United Nations Space Command.

In HE Ammunition, an explosive compound is added or mixed in with the standard type of gunpowder. After the bullet has been fired from the weapon and has hit a target, the compounds inside the round will ignite, thereby offering a potentially larger entry wound, a deeper impact wound, and a dangerous exit wound. The rounds are therefore useful for placing exact shots at the more vulnerable parts of the body, namely the head and torso.

HE rounds are effective in both Anti-Material and Light Anti-Armor purposes, capable of cutting through both flesh and alloy with ease.

Against the Covenant
When used against the Covenant infantry/vehicles, HE rounds are more effective than other ballistic ammo, provided the shooter aims at either the head or torso of the alien (neck/abdomen against Hunters). These rounds are extremely effective against Hunters, and are semi-effective against Covenant energy shielding.

Against Flood
The HE ammo is extremely effective against all types of Flood, capable of tearing through the decomposing Combat Form, exploding the destructive Carrier Form, and easily killing groups of Infection Forms. Still, for the sake of practicality, carry a reliable close range weapon, as HE ammo is more effective at mid range and weakened at short range.

Appearances
HE ammunition is most often used in Anti Vehicle weapons, where its explosive capabilities renders it particularly effective against alloy steel. The only handheld weapons that use High Explosive ammo are the M6C, M6D, and M6G Pistols. All three use M225 Semi-Armor-Piercing High-Explosive.

Trivia

 * In Halo: Combat Evolved, when you fire a Pistol round at a solid surface, you will see a small burst of light, which probably comes from the explosive compound.