ROTARY MACHINE GUN COMPARISON SPECIFICATIONS. M-134D MINIGUN. Caliber: 7.62x51mm NATO. Rate of Fire: 3,000-6,000 RPM. Weight: 85 lbs (approx.). Barrels: 6. Power Source: 24V DC. GAU-19/B .50 CALIBER. Caliber: .50 BMG (12.7x99mm). Rate of Fire: 1,000-2,000 RPM. Weight: 140 lbs (approx.). Barrels: 3. Power Source: 24V DC or Hydraulic.