Model-wise, I think it is more likely that the drum mag on the V308 is modeled bigger, since the V308 is the primarily fictional weapon here.
Stat-wise, I can see the point of using the caliber to indicate bullet destruction potential, though I would prefer if it is more clearly stated in the infobox that the ammunition type is supposed to indicate destruction potential. It would be even better if we find some better, more direct stat to use as the "unit of destruction capability".
Trivia-wise, the current trivia is mostly just speculation. I'm going to give that a rewrite.