The following is constructive criticism, not bashing!
Ok, lets start out with the positive!:
First of all, I am happy to announce that the ingame Mkb42(H) behaves closely to the real thing (Judging by StG), which means it basically owns every other weapon in the game, just as it does in reality as-well.
Now to the negative part:
Giving every 2nd guy an Mkb42(H) is not only extremely unrealistic, but it's also very bad for gameplay! The Germans are litterally bulldozing the Russians now on every map. Every 2nd or 3rd guy carrying one of these guns is just too much firepower for the Russians to handle.
I strongly suggest you limit the Mkb42(H) to 2 pr. map at max, and that's for 64 players servers, otherwise the disparity in firepower is going to seriously hurt the Russian side.
Some maps don't have the Assault Class available and the ones that do usually have the class slots limited to 2.... on a 64 server, I've seen it open up to 4 slots, but that's it.... that's hardly every 2nd/3rd guy on the team.... that's 2-4 players out of 32.... 4-8 players out of 64.... that is if both the Russian team have all their assault players leveled high enough to get the enemy weapon load out ..... AND, only if they all decide to pick the MKB (both Germans and Russians)
So usually a maximum of 8 MKB's.... at best, in a 64 player server (usually 4 max) is really not that excessive.
And 32 players or less, you only have to worry about 2 MKB's.... that is if you have players actually fill the assault slots, which I have seen free a number of times during matches.
Now in regards to how over powering it is?
It's really not that over powering and has a number of disadvantages.
#1 - It has a unique sound and thus, very easy to locate and track down the guy using it.
#2 - In my experience, it stopping power is not as good as the MP40 / MP40-II. I've dropped more players with less rounds with the MP40 than I have with the MKB.... even though looking at the books the MKB should be more powerful than the MP40, in the game, I seem to have to hit my target with more bullets with the MKB than with the MP40.
#3 - Once it has that little scope on the top of it, which is kind of useless, you lose a lot of viewing area on your screen and becomes a bit of a hindrance... you then usually see these guys using the scoped MKB as a sniper rifle, holding back, using the semi-auto and plinking off players from a distance. Is that an advantage? Not really since they're no longer using the assault class as an assault class.
#4 - The PPSH, imo, is far more superior than the MKB, both in rate of fire, power, 71 round ammo drum and eventually, select fire capability... and no worries about having a scope slapped on the top.
The MKB does has some advantages, like being able to have a bayonet and decently accurate in semi auto.... but I think people blow it's capabilities way out of proportion.