How to Make an Airsoft Machine Gun (AKA Halo Mobile Turret)

Airsoft doesn't get any better than a cloud chamber BB machine gun, aka Cloud BBMG. This design has an incredible rate of fire. If you've got a full charge of compressed air, it can easily fire more than 50 rounds per second at a 350 ft/s muzzle velocity. Since this is a legit airsoft build, it should be handled safely with the same care as any other airsoft firearm, and you should be wearing the same protective gear—protective mask, safety glasses, etc. My video details the build of this beast, which is meant to use plastic airsoft pellets.

There's no moving parts to feed the pellets into the barrel. Instead, it functions on the principles of differential gas pressures. When you pull the trigger, the high pressure from the compressed air enters the reservoir that contains the pellets. That rush of air forces the BBs to pounce around randomly, while at the same time increasing the internal pressure of the reservoir. Because the barrel is a clear opening from the reservoir to the comparatively lower pressure of the atmosphere outside of the gun, the gas escapes though the barrel and sucks the pellets in with it. Since there are no mechanical parts, the rate at which pellets can enter and exit the barrel is virtually unlimited.

If you want a higher duration of fire, you can increase the size of the air chamber. My version in the video above is capable of about 5 seconds of constant firing at 60psi, which equates to about 200 to 300 pellets fired.

If you want to try this build out, it will cost you around $50. Not bad at all.

Parts List

• 4' of 2" pressure rated sch40 PVC
• 4' of 1.25" pressure rated sch40 PVC
• 2" end caps (x2)
• 2" 90-degree elbow
• 2" 90-degree street elbow
• 1.25" end caps (x3)
• 1.25" couplings (x2)
• 1.25" x 0.5" threaded reducer
• 0.5" threaded plug
• 6mm ID x 3' aluminum tube [a 6mm ID steel automotive brake line my be used instead]
• Rubber tire valve
• Air compressor blower valve w/ threaded ends
• Close brass pipe nipple [to fit blower valve]
• Hose fittings [to fit blower valve] (x2)
• 1' air compressor hose [matched to hose fittings]
• Hose straps [for compressor hose] (x2)
• Large hose straps
• 1" foam pipe insulation [or a wood block fitted for chamber support]

Note: This fully automatic airsoft machine gun was inspired by the mobile turret in Halo.