You can make your own fake gatling gun

 I hadn't added an ammo belt yet to this cosplay minigun, but the delinker does have the ammunition chute dock on the side here. By this last Sprig, my minigun design had really evolved into something fantastic. You could take this bright orange one all apart without using tools, and just as easily pop it all right back together. The barrels are metal conduit, the rest is 1/4" thick plastic.

A costume minigun should have barrels that spin when you squeeze the trigger, this one that I developed does! Want to build your own costume or event Gatling gun? I've got CAD files, PDF's, and trace and cut JPG files for you at www.mrminigun.com

One of my early minigun gatlings

I based this one on the gun in Predator, kinda. Too small, too little detail but it WORKED.  Non-firing, but the barrels spun at a good 900rpm with a fresh drill battery attached. I went on to build literally hundreds of these crazy costume Gatling gun. The barrels are 1/2" conduit, the body cut from 6mm thick ABS plastic from Interstate Plastics in Sacramento.
YOU can build a much nicer one, get the CAD files for this Minigun Gatling Dummy at www.mrminigun.com

M134 Mini Gun With Pack and Chute, Just $999?

Here's the First and Only full setup M134 (Westinghouse type machine gun) costume gun you can get, off-the-shelf, in the entire World.
Overall size is 34" long, 12" wide, and 11" high.  
The gun itself weighs almost sixteen pounds.
All major parts are minimum 6mm thick ABS, and CNC machined to size.  
There are NO vacuum-formed or cheap cast parts.  
The 20" barrels are steel, and they rotate at up to 500RPM, powered by a hidden 18volt rechargeable power pack (included) that docks underneath the M134 mini gun, out of sight. 
The authentic ammo chute and back pack complete the show: full sized real US Military ALICE frame pack and heavy duty ammunition box. 
The 5lb, 52-inch flex feed chute is adjustable for length, and is quick-detachable from both the gun and the back pack.
The port on the ammunition pack can be mounted in multiple locations and positions, top, bottom, left or right.

  The ammo chute has four positions it can mount in on the top or bottom of the unit, pointing to the left side or the right. Also, the chute also has three possible mount locations on each side, pointing up or down. 
So it can be easily tailored to a particular costume or preference.

The ammo chute just pushes into the port, and auto-locks into place. Squeezing two tab ears together releases it, just like on a real M134.
 The ammo chute itself can be shortened as needed with an included Phillips driver.
 Extra links will be available to make super-long chutes (unwieldy, but look awesome).

 The ammo Pack kit will come with the connector that goes on the gun. 
This will only fit my Mini's built from September 2014 on without mods.

 More info at www.mrminigun.com

M134 $999 at Mrminigun.com

 Here's the latest motorized minigun from www.mrminigun.com

 It's 34 inches long, 12" wide, and 11" high assembled. 

 And we say assembled, because it's a knock-down-able modular design:

 it all comes apart into components with simple snap-locks on the carry frame, motor, and delinker. 

The 20" steel barrels are gear-driven, with massive CNC-cut teeth over a 1.4 inch tall. 

 The minigun also features a safety clutch, so the barrel disengages from the drive if obstructed, without damage. 

The virtually unbreakable ABS Engineering Polymer parts are all minimum 1/4 inch thick, with chembonded construction for rugged, long-life usage.  More info at www.mrminigun.com