The following special rules apply to Chimeras used in Mechanised Infantry Companies. They may also be used for Chimeras in a standard Imperial Guard army as long as both players are aware of the rules before the game starts. In all cases, these rules take precedence over the rules in the Warhammer 40,000 rulebook. In particular, they replace the rules for 'Troops Firing From Vehicles' on page 82 of the Warhammer 40,000 rulebook.
Chimera Special Rules
Source: Codex: Armageddon, p. 29