Is that an upgrade, or another type for another kind of application? Not every GI Joe got a M249 when those were introduced as squad weapons: M16 still soldiers on as the individual fighter's weapon.
When Nog totes a First Contact rifle in DS9 "Empok Nor", it looks (and I think is supposed to look) like he's brandishing a machine gun in a ridiculous bit of overkill, while the serious security folks just carry standard assault rifles of the good old TNG "The Mind's Eye" type.
Applying that retroactively, it would make good sense for everybody on the E-E to pack machine guns against the Borg, even though they would continue to use the shorter, lighter, more practical assault rifles against Klingons and Romulans and Breen and Jem'Hadar and other lesser opponents.
That YouTube snippet sounds interesting... Any further keyword suggestions beyond "DS9 Dominion War"?
Timo Saloniemi