.450

.450 is an ammunition caliber used in the Sniper Rifle System 99C-S2 AM. It is not standard to the series, and is considerably smaller than the standard 14.5mm rounds, but are lighter, and still capable of dealing considerable damage to a target. It was used by Spartan-II Linda-058 when Blue Team captured Colonel Robert Watts.

It is unkown if this round bears any relationship to the .45 round used by some Earth militaries in the 20th and 21st centuries in weapons such as the Colt M1911 pistol.

Trivia

 * This is not the sniper rifle's default ammo size. The regular size is 14.5mm, but Linda converted her sniper to use this caliber round.
 * ".450" means that this bullet is forty-five hundredths of an inch wide. This means it is about 11.43mm.