WTF? Is he holding it by the barrel? Yeah, it's got some kind of heat shield, but still.
It's hard to tell from that image, but it's not uncommon for light machine guns, intended for use while carried like he is using there, to have some form of grip forward of the receiver, and there is definitely some form of cowling over the barrel, probably to aid in heat dissipation.
In real life, carrying and shooting a belt fed machine gun from the hip is not a good idea, no matter how dramatic it looks. It can be done, but without some form of hand protection (even a simple glove would do) holding onto that cowling would get uncomfortable fast, and likely painful in just a minute or two. Then again, if they are putting down suppression fire for a couple seconds, or similarly shooting briefly at a massed group, then they might be able to get away with it.
Since I've never seen the movie in question, I can't say anything about the situation. I can say, however, that action movies from that era cared more about good looking shots then realistic ones. Not too different from action movies today in that sense, really......
With all that said, it is unlikely that Erwin, he who has balls bigger then Bahamut, will be using a machine gun anytime in the course of this story, so really, we can instead focus on the sorts of weapons he might actually use. Perhaps he has a .40-70 revolver sufficiently overbuilt for handling hot-loaded ammo, for instance; that should cover all of his hand cannon needs, since such a weapon is capable in real life of killing an elephant, much less most younger dragons......