The biggest flaw is that maps exist that not only allow ramboing, but reward or leave it as the only option for the MG on the offensive team because there is only cqc. There is very few places for an offensive MG to setup on Apartments that you don't have to rambo to get to first (lots for defensive though).
I don't see MGs ramboing on the big maps like bridges, Winterwald, or medium sized ones like Fallenfighters or Red October Factory that are more like ro1 maps in terms of size/ open areas where they can setup. Vote for those maps instead of cqc maps.
On servers with map voting, when people vote for apartments for the 3rd time in 5 matches I'll change classes and start ramboing as MG just to end it quicker/make it unfun so we don't keep playing it every other match when there is over 20 viable maps to pick. Cause I consider voting for apartments that much a form of griefing and its worse than spawn camping in my books.
Best 4 ways to kill rambo MG, remember they are ramboing which is loud, you should know they are coming unless you are the first person they shoot.
1. Grenades, prime it and toss it around the corner, if you know how to prime nades and how to throw them properly with about 1-2 sec left on the fuse, no one can survive them, I use this trick to take out non-rambo mgs, up a flight of stairs all the time.
2. PPSH, it fires faster and is way easier to aim 9 out of 10 times an equally skilled ppsh player vs rambo mg and the ppsh wins
3. Melee when they walk around a corner/from behind. Since a rambo is walking and firing, he's moving slow you can often run a small circle through different rooms to flank him. If your caught infront of them duck and weave to a side, some rambo mgs aren't too good about turning. You can sometimes smoke a room before he gets there and try to ambush him too.
4. Aim for the 3 1 shot areas (Heart, head and nuts) or if your using a bolt action rifle just hit them once in the chest and they usually die, but you gotta do it fast. I have a lot of bolt kills like this on rambo mgs.