Universal Miniguns!

Modular design, they are rugged and reliable, and water-resistant. 

Pictures here, the guns will soon be available at: www.mrminigun.com

 29 CNC machined parts, and a few well-chosen plumbing aisle components.

 All chem-bonded using the excellent Oatey Black ABS adhesive.

 The mount is universal-fit, so you'll need to decide where to drill to mount it.

 The gun is 31 inches overall length, assembled.

 It is made of four major assemblies, that just snap together.

 I designed and make the massive gear train myself.

 The DC drive motor for the minigun has a planetary transmission with straight-cut steel gears inside.

 Here's the motorized vehicle minigun, taken apart.  It can run on any DC voltage source, from 9-24volts.

 The minigun is 31 inches overall length when assembled.

 It can be taken down as shown, without using any tools at all.

 The steel barrels are solidly assembled, like the rest of the M134.  Notice the complete lack of fasteners on the barrel.  It's 100% Cold-Bonded construction.

 Paint is off the shelf black Krylon, nothing special.  They could easily be repainted or touched up.

 The simple core of the minigun has some very well-thought out geometry.  It has few parts, fewer fasteners.  If it isn't here, it cannot possibly give you grief.

If you ever manage to wear one out (I doubt it in a normal lifetime) spares are standardized and available.