Ultimate Lego Gun: Longdraw BC16
Some background info after the jump...
The concept for this gun came from my experience with other Lego guns. I found that increasing the number of rubber bands wasn't the best solution to adding more power, because more rubber bands made it harder on the gun and didn't increase the power beyond a certain point. Through my knowledge of physics, I knew that Kinetic Energy equals force times distance, so a way to increase KE without adding more force was to make the draw longer. I also found that having a smaller firing pin gave the gun more power, so I set about to create a gun with a long draw and a small firing pin.
The mechanism for the gun works like this: As you cock back the pump, you push back the firing pin. When the firing pin is almost at the back, the trigger catches it and holds in in the back area. As it goes all the way back, the firing pin hits a special piece that releases a bullet from the clip. As you cock it forwards, the firing pin moves forwards until it hits the trigger, and while it moves forwards it pushes the bullet forwards (chambers it) and locks the rest of the bullets in the magazine so they won't fall down behind it. Then the pump moves to the front of the gun to get out of the way. When you pull the trigger, the firing pin accelerates through about 7 inches (17.5 cm, 22 stud units) of space, flinging the bullet at high velocity. To see a video of the mechanism, see my other post.
The Longdraw BC16 is named for 3 things.
Longdraw because it has a longer draw than most Lego guns (7 inches, 17.5 cm, 22 stud units).
BC (Brick Cannon) because it fires large Lego brick rounds.
16 because each brick is 2x2x4 stud units for a total of 16 cubic studs.