I used the term to describe what I hear on video. I hear what sounds to me like a 30 round 5.56, interspersed with much longer bursts from something larger. Gut says 7.62. Not quite barrel melting bursts, but longer than US doctrine suggests. I have both calibers, but the acoustics aren’t as good on these videos as what I hear on the firing range.
^^ My opinion, fwiw.
I’ve been speculating that the long pauses between belt dumps were because they may have been changing the barrel. 15 second pauses to reload the belt are a bit long even for new gunners, but adding a barrel change to it would explain it.