Echo1 Polymer PMG-5 JP-143 Airsoft AEG Minigun Elbow & Knee Pads This is a metal gearbox

This is a metal gearbox

These start out as a blank body directly from Empire

That's right

Cale Leiviska had this to say

Echo1 Polymer PMG-5 JP-143 Airsoft AEG Minigun Elbow & Knee Pads This is a metal gearboxFeatures Durable heavy duty metal & nylon fiber receiver construction Lightweight nylon fiber furniture and magazine Stress resistant metal gearbox Adjustable hop up Quad Barrels that rotate at a rate of ~1000+ rpm Large battery space ideal for high capacity 11. 1V LiPo batteries Mechanical firing system that fires out the top barrel, the electric motor is used only to rotate the barrel assembly Equipped with a 3 and 9 o'clock Picatinny rails for