Time to perform some thread necromancy.
Looks like (please notice the emphasis on 'looks', as I can't read/speak Japanese), after all, there isn't any gunpowder on Britannian arms. The old-fashioned handguns displayed here (and featured on the Code Geass DVD-1 extras) have some sort of electric/electronic contraption replacing the bolt carrier group, making the weapon some sort of miniature railgun or Gaussian gun.
It sort of explains why the Japanese, despite having
Kongo-class warships and
Leopard 2-type MBTs (Main Battle Tanks), still have pistols that look like WWII model-offshoots, and why the Britannian police still have Webley revolvers instead of more modern and higher capacity, Walther P99-lookalikes. They simply don't need the modern handgun architecture (although I wonder why they don't lose the revolver design...a modern pistol's magazine actually can have double more capacity than a cylinder can ever hold).