A character may fire a ready firearm in single-shot, semi-automatic, or burst-fire mode via a Simple Action If a character has one weapon in each hand, he may fire once with each weapon by expending one Simple Action
Meaning you shoot both of those guns with that same single action.
SR4A page 150:
"
Attacker Using a Second FirearmCharacters can use two pistol- or SMG-class weapons, one in each
hand, firing both with a single Simple Action. Doing so, however, requires
that the character split his dice pool between the attacks. If two
separate skills are being used (Pistols and Automatics), use the smallest
dice pool. Split the pool before applying modifiers. Two-gun attacks
also negate any dice pool bonuses from smartlinks or laser sights.
Additionally, any uncompensated recoil modifiers applicable to one
weapon also apply to the other weapon."
RC page 115:
"Characters with Shiva Arms can choose to wield multiple
weapons (firearms, melee weapons, or a combination of the two)
in combat (Holding Weapons, p. 161, SR4). Weapons wielded
in an off-hand suffer the usual penalty; this applies both to firearms
( p. 142, SR4) and melee weapons (Off-Hand Weapon, p. 148, SR4). The character can
use the Fire Weapon action (p. 136, SR4) with firearms in their
extra hands, though the character must still split their dice pool
between the firearms, and any penalties for using firearms in offhands
still apply."
Meaning a character with six guns in six hands can fire all of them with
one simple action by splitting his dicepool sixways.
