There’s nothing quite like [Elliot]‘s cherubic sense of wonder and maniacal laughter after he tests his fully automatic AA battery-launching air gun. That fires 600 rounds a minute. At 200 feet per second.

We need to take a minute and say [Elliot]‘s gun is stupidly unsafe. He used PVC pipe to hold air pressure, so that may… explode one of these days. Also, the AA batteries coming out of the end of the barrel have the same kinetic energy as a .22 rifle bullet.

The mechanics of the gun is a simple blow forward bolt. When he pulls the trigger, the bolt – and battery – are forced forward due to air pressure. After the bolt has cleared a plug, air is allowed to flow through the bolt pushing the battery along with it. Once the pressure in the barrel is back down to normal, a spring forces the bolt back into place and the 23 round magazine loads another battery. Simple, really. [Elliot] posted some pics of his gun on the spudfiles.com forum.

The gun is accurate to about 100 yards. It’s a very impressive piece of engineering for a bit of PVC pipe, but we don’t feel the need to copy this one. Check out the videos after the break to see this thing in action.

Good old [Jörg Sprave].

That guy just doesn’t quit building insane slingshots. If he’s not honing his machete slinging skills in preparation for the zombie apocalypse, he’s blowing out car windows with giant steel balls.

The huge cannon you see above is modeled off a small slingshot he made a while back, which fired 8mm steel bearings. In its larger form, the slingshot is said to be ten times the size of it’s smaller brother, firing 80mm steel balls with incredible force. In the video below, [Jörg] and his friends cart the slingshot out to a huge empty field where they run it through its paces on several different objects. Their first shot flies about 220 yards into a high tension tower, after which the boys aim their sights on an old car.

The power with which the slingshot fires is definitely impressive. With a few well-placed shots, the car is pretty much done for.

Now that we’ve seen [Jörg] fire off saw blades, machetes, and giant ball bearings, we can’t wait to see what comes next!

This collection of gauss weapons use rare earth magnets to accelerate projectiles to damaging speeds. They work using the same concepts as a coil gun, but instead of just one projectile travelling along a length of guide track, there are many projectiles that work in a chain reaction. A series of magnets are placed at equal distances along the track. Each has a couple of large ball bearings on the muzzle side of the magnet. The first ball bearing is fired using mechanical force – like a spring mechanism – and accelerates as it approaches the magnet due to the attractive force of that magnetic field. When it impacts the magnet it sends one of the ball bearings on the opposite side down the track where it will accelerate when it nears the next magnet in the chain. The weapon above achieves a final projectile speed of about 68 miles per hour, breaking six fluorescent tubes in a row on at the right side of the apparatus.

Still prefer rail guns that use electromagnets? Check out this gauss pistol kit that is about as powerful as a BB gun.

[TheBserk] made himself a set of auto-locking and auto-retracting hidden blades inspired by those in the game Assassin’s Creed. As you can see in the demo (and build guides) after the break, they work really well. We don’t like the idea of sharpened metal ramming its way past our wrists. But it’s not the first time we’ve seen dangerous arm-mounted hacks.

Reminiscent of Taxi Driver, [TheBserk] uses drawer slides from the local home store for his build. They are cut to length, and modified using springs for the automatic action. There is a lock to keep the blade extended, and a pull-wire to actuate it. Although dangerous, the build is well done. We think someone has mechanical engineering in his future, and possibly a trip to the emergency room.

The demonstration

Build guide part 1

Build guide part 2

[Thanks Kentaro]

a Ruler, rubber band, and a pen make a bow and arrow? How about tape, a ping pong ball, and a lighter coming together to make a ‘Zooka. We didn’t think such destructive weapons could possibly be made from office supplies, but the famous [John Austin] is here to prove us wrong. He’s been miniaturizing toys and their munitions including Transformers, Star Wars, Jurassic Park for years. With the resent release of his new book, he’s left us the grace of a few teasers.

[Thanks Chris]

[Limor] of Adafruit Industries and the Ice Tube Clock has made her own open source non-lethal weapon: The Bedazzler. After attending a conference by the DHS where she saw the big-budget Dazzler, she decided to make her own. Thirty-six LEDs, six switching FETs, a Boarduino, and a former flashlight later, the Bedazzler makes a better rave toy than a weapon. It doesn’t work as-is, but we figure it will only be a matter of time before someone hacks this to make people… umm hack.  See the video after the break.

[Alexander] sent in his entry into a “creativity contest” at his university. He and some friends put together this dry ice cannon.  Take note of the creative mechanism they used to mix the water with the dry ice. A large amount of gas is expelled as soon as the two begin to meet. If the gas is supposed to escape through the same opening, it is difficult to get all the material through. They have added a second opening just for the exhaust during mixing. Great job guys. How about some downloadable plans.

[via Acidus]