The inventor seems to have used a magazine and bolt design similar to the ancient Chinese repeating crossbows.

From the inventors website ...

The specification I devised called for a full auto-firing rate of 1 bolt per second; with 6" of draw length and a minimum of 30lbs draw weight. The magazine was to house 10 bolts 9" long. The bow was to be capable of discharging the full magazine with imperceptible slowing down and have an effective range of 25 yards.

The draw length is limited by the throw of the crank that pulls the bow carriage plus the relationship this has with the near stall torque that can be pulled out of the motor / gearbox assy. The need to maximise these relationships must be balanced against the voltage / number of batteries / weight.

The above was achieved using 8 AA rechargeable NiCd batteries giving 9v.

Hat Tip: SaysUncle and egosumquisum

AR 15 lower receiver, 170lbs built in easy cocking mechanism 3 rails. 425 grain arrow 420 fps. TAC 15 Tactical Assault Crossbow

I think this finally ends the 5.56mm vs. 6.8mm vs. 7.62mm debate. Clearly a 425 grain bolt beats them all!

Actually “tactical” crossbows have been around for a long time. Special forces were known to use them as weapons or as zip line launchers. I would be surprised if they are still in use as weapons.

Indian Black Cat commando with crossbow.

Hat Tip: Shawn B for the info. Photos from erikbarnes25

Click to expand.

It can be cocked in three seconds and fire a bolt at a speed of 370 feet/sec [ I know nothing about crossbows so I am not sure how revolutionary a 3 second cocking action is].

This video demostrates how it works the action works.

Brenzovich are importing the Twinbow but I am not sure who is actually selling it in the US. Arrow In Apple are selling it in Europe for 1449 Euros.

UPDATE: James has written an interesting post on how this crossbow compares to regular crossbows. It is worth reading.