Yes, that is what the books say. Unfortunately, that's one of those completely arbitrary rules that is not consistent with the rest of the system. Every other pistol that fires a three-round burst receives a +3 recoil modifier (if it doesn't have some other form of recoil compensation). Other than for the reason of satisfying someone's sense of game balance (totally subjective, mind you) there's no reason why the Thunderbolt, under my definition, should be treated any differently than any other pistol when it comes to recoil modifiers. +1 per round.

My idea of it is that the Thunderbolt is based off of an existing frame, which would defer some production costs, although at some point the production line has to split to accomodate each model of pistol (fairly early on because the frame has to be machined differently). The picture is just a doctored Ruger KP90D.

The "magazine" is still there because the Thunderbolt is an electronic pistol. That space is no longer used to store ammunition, but instead the batteries that power the pistol. In my mind, the battery pack only occupies a little more than half of the mag well, while the electronics occupy the rest. Battery packs can be changed in the same manner that you'd change a conventional ammunition magazine.

The lever above the pistol grip is multi-functional. It acts as both a manual safety and as the latch that unlocks the action for reloading. When that lever is tripped, the rear of the barrel block (the stainless steel part of the pistol) slides upward under spring pressure and is hinged at the muzzle (the black circle near the muzzle). This allows access to both of the over/under chambers. Ammo stacks are placed in each chamber and the action is closed. At that point, the pistol is ready to roll. Needless to say, it's not particularly easy to reload quickly, but that's just a downside to Metalstorm.

In this picture, there are also integral ports (gas vents) drilled directly into each muzzle of the barrel block. Another effective form of recoil compensation on a pistol like this is to allow the entire barrel block to reciprocate on top of the frame, similar to a conventional semi-automatic pistol. At 90,000 rpm, that would easily delay the effects of recoil long enough for all bullets to clear the muzzle.

That's exactly the problem: it's unlikely the electricity generated from a single trigger pull would be enough for 12 rounds on full auto.

And then there's the issue of having a quick, field-expedient way of replacing the piezo which would reside inside the trigger mechanism, should it fail. It's a two-second operation to change a battery pack that will last for literally thousands of rounds.

Here's the patent. It's specifically for Glock pistols.

Cannon Companion doesn't specifically say that the Thunderbolt fires three rounds per burst. However, since the BBB specifically defines "burst-fire mode" as a three-round burst (pg115), and since the only weapons that violate that rule (the HV series) explicitly say so in their descriptions, it's reasonable to assume that the Thunderbolt is the same.