trigger #1- mounted at the hilt of the sword handle, this trigger is for quick access to the gun when aiming isn't completely essential.
trigger #2- mounted at the handle of the gun itself, when using this trigger the wielder can put their other hand on the swords handle, this trigger is for when the wielder has time to aim better. (angel would be in the position of the 3 model down when using trigger #2. it would actually be very easy for your wrist just to turn the sword horizontal and use your left hand for the gun handle while your right hand holds the sword up from its handle.
The revolver also serves as a hand guard (because of its position, unconventional to the usual gun-blade), and its weight balances the sword out very well.
Pistoning blade- the back section of the blade pistons up or down, changing the swords center of gravity (center of gravity is KEY to the following concepts). This is useful for weight management.
when the piston jets the blade up, it is useful to increase the speed of the blade for a quick/powerful slash otherwise unable to attain without a piston.
when the piston brings the blade down, it is useful to bring the blade back from a swing quickly.
other wise it could be used to further split an enemy in half when the main blade has gone through them. the possibility's go on, be imaginative