A while back I was on a shoot in a bullet factory, and had a bit of time between setups to run around in the production facility to record some of their machines... I gave no idea what the machines are called, but the make some awesome sounds. I used a Sennheiser 416 going through a Sound Devices 302 and into a Sound Devices 744T. I trimmed the heads and tails of the clips, but otherwise performed no mastering or post of any kind.
Enjoy, have fun.