Or a 66mm SRAAW for that matter and that is a lot more "manageable" inside a car
Having been behind the wheel when a belt-fed Minimi was fired out of the boot, I wouldn't recommend firing anything out of a moving vehicle. We were finding empty casings in random places for days and the ringing in my ears went on all day! Damn good fun though.
Still, back to the thread, it's not uncommon for a bomber to blow himself up. It's either Darwinism at work - as here, or the fact that they've built a bodge job which is unstable and when combined with agricultural handling (there's a phrase that takes me back!) it is a recipe for disaster.
It reminds me of some AC130 footage I saw a few years back - it's probably on You Tube now - of an insurgent IED team burying an IED which went boom prematurely. There was one survivor who had been stood away from the rest and who was seen to be marginally less than happy at rummaging through the smoking hole to see what was left.