M228 Semi-Armor-Piercing High-Penetration
From Halopedia, the Halo wiki
The 12.7x40mm M228 Semi-Armor-Piercing High-Penetration (abbreviated M228 SAP-HP) is a type of .50-caliber round used in the M6 series of sidearms.
It is somewhat rare and more of an exotic round due to its rarity of use compared to the M225 SAP-HE.[1]
Due to the semi-armor-piercing nature of the round, it is likely coated in a hard metal such as steel but deforms shortly after impact to prevent the bullet from leaving the body and causing accidental casualties. The filler is likely a hard or heavy metal, such as tungsten, which would provide the extra force and penetration this round boasts of. It is possible that such synthetics such as Kevlar are used as well.
In Halo multiplayer, the M228 SAP-HP is drastically underpowered, taking almost 13 rounds (which is one round larger than the magazine of a pistol) to kill a fully shielded Spartan or Elite.
