First, a key difference: instead of being loaded by a bolt mechanism, this blaster is breech-loaded. So if you decide to make barrels for Nerf darts, you'll have your very own double-barreled shotgun.
The rear handle operates the air pump, which sits inside the plastic air chamber. Yep, the entire red section is a large air tank. Larger than the original Marshmallow Blaster, at least.
The trigger assembly, disassembled. It works the same as the original version - a plastic piece seals against the rubber, and is held in place by the plastic catch. Once that is pulled out of the way, the red piece is pushed forward by air pressure, and the blaster fires. Notice that the ends of the air chamber simply unscrew.
Here's the firing pin/rubber seal. This gets sandwiched between the tank and the end cap to seal everything up.
I'd show a test firing, but I don't have marshmallows that fit tightly in the barrels! So, it seems I'll just have to mod this and compare to the original! Stay tuned!