Shredder rounds are one of the special type of United Nations Space Command projectile rifle ammunition.
Shredder rounds are designed to splinter on impact, tearing through light armor and "shredding" targets into ribbons. They are usually fired from assault rifles as a replacement for armor piercing rounds. However, shredder rounds have a severe lack of penetration power and they are all but useless against Covenant personal shields. They are most often used against massed enemies with light armour such as Grunts.
Magnetic Accelerator Cannons can also be equipped with a round that acts similar to a shredder round. The UNSC Pillar of Autumn was the only known UNSC ship to be armed with this type of MAC ammunition.
Shredder rounds are the type of ammunition was often used by the SPARTANs when they ran out of AP ammunition.
In the Lambda Serpentis System in 2535, the SPARTAN-IIs of Blue Team switched to using shredder rounds after exhausting all of their AP rounds when gunning down a horde of Unggoy. Another instance is when Blue Team is at Cote d'Azur, engaging a pair of Hunters in a museum. The SPARTAN-IIs discovered that the AP rounds were ineffective against the Hunters' armor and resorted to using shredder rounds. The SPARTAN-IIs fired the marble floor beneath the Hunters using shredder rounds.
The real world variant would be modified JHP, or Jacketed Hollow Point ammunition. This is a variety of hollow point bullet. The bullet consists of several segments of a hard metal that is welded together with a soft metal such as lead. The welds acts as weak points, so that on impact, the bullet should seperate along the welds into component segments. This spreads the damage over a larger area, but it also decreases the penetrating power. These rounds are surrounded with a fluted or perforated metal jacket in order to provide optimal fragmentary habits, as opposed to a haphazard disintegration which would do less damage.