.450

.450 is an ammunition calibre 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.

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.