The C4 Semi-Automatic Crossbow is the first semi-automatic crossbow which is as powerful as a regular lego crossbow. The crossbow can fire 35 feet or more, and has a 4 round capacity. I came up with the idea for a semi-automatic lego crossbow when I was trying to create a gun which could fire the Y1 Shotgun Shell powerful enough to separate it, which would be a crossbow, but also had a higher rate of fire (semi-automatic). The prototype which fired the Y1 eventually failed, but 5 months later, I readapted it to fire my standard crossbow round( (2x4)F ), which worked out very well. The gun works very well, and has a good rate of fire, and a good sight (similar to the M16 sight). It is powerful enough to go through paper, and ricochet very far. How the crossbow is semi-automatic but still looks like a crossbow is that the cover that goes over the magazine is wider than it would be on a normal semi-auto, which allows the rubberbands to still go on the trigger at an angle. This allows maximum power. The way the firing rubberbands work is that once one shot is fired, its corresponding rubberband flies to the front of the gun, and below the firing runway, where it stays. This prevents the used rubberbands from blocking the next shot.
TO BUILD THE IMPROVED VERSION, THE C4.1 ------> [http://www.instructables.com/id/The-C41-Lego-Semi-Automatic-Crossbow/
MY WEBSITE: http://sites.google.com/site/bblegobrickworks/Home
For the C4.1 Semi-Automatic Crossbow (coming in a few weeks), these changes will be made: The top of the magazine holder will be altered to be more sturdy (The C4's hasn't broken yet, but its just a precaution), the firing capacity will be increased to 5 rounds, a stock will be added, and a bipod will be added.