Ill do some test this evening. I csnt believe that works. Im 100% sure that you will get suppressed if you xharge max range (which is greater than the sight range of the mg)
Let me guess the result of the test.
Every MG is able to stop any squad charging frontally if they do so through grey cover, with fog of war removed (so you have vision at max range).
What probably happens in game:
-You don't have vision so you start shooting at MGs vision range.
-Through mid game to late game, grey cover disappears transforming into yellow cover.
-Sometimes reload cycles screws you. If you can't suppress in 2/3 bursts, the MG sucks.
-Squad charging is not at full health. Killing models on approach on first burst makes it to take longer to suppress a unit.
If you don't hit vet2 with vickers, you are screwed in the late game as far as suppressing squads go.