I just had a glitch where I would be holding down the minigun's fire button, but it wouldn't fire at all. The barrel would spin, but no bullets came out.

What eventually fixed it was that I ADS'd and that made it fire again.

I've been running into the Same problem but not just with the Mini Gun, i've had this happen with other weapons where I hold down the fire button and nothing happens. Sometimes it also stutters as if it's missing the input from the controller. Can be very frustrating.

Note* This has happened in Private games with only one other friend with and excellent connection.