Think of a turn as having three stages. Most actions take place only in the first stage.
Think of a turn as having three stages. Most actions take place only in the first stage. Any second or third actions take place in successive stages after this. Thus, if one guys is shooting a gun three times in a turn while his opponent only fires once, they would each determine initiative normally and then each take their first shots. Then, the guy with the multiple actions would resolve his second and third shots. If the opponent was also firing multiple times, initiative would be resolved normally for each action: everybody takes their first actions, then everybody takes their second actions, then everybody takes their third actions. There are no special initiative penalties simply for performing multiple actions.
Below are some suggestions on optional rules for multiple actions. These are based on the theory that multiple actions take place almost simultaneously.