Why does the 240 and the MG3 have that delay?

So this is a repost from a question I asked a few weeks ago on the steam forums, and nobody could answer me there, so I figure i would ask it here.
I have started playing primarily as a machinegunner a for a few weeks now, and can someone explain why the 762x51 mgs have these strange delay before firing?
The 249 and the PKM both dont have it.
I just cant figure out why this mechanic is here.
Is the delay here purely because of balancing the 762x51 mgs, or is it something other than this?

Also I would really like to ask why is it that the M16a2 has the long range aperture hole, when the a4 version has the close one? It makes using it a real pain (albeit satisfying). Why not change it to the close aperture like the other model?
Maybe also, seeing that the a2 has an specific longer range scope, maybe they could add the Aimpoint 2000.
I dunno, I think it would be cool.
And as side note, I would really like to see an m60e4 or a mk43 mod 0 or a Stoner variant get added to the roaster in the future.

Anyways, still cant get enough of the game, aside from the godlike grenades and molotov that the bots throw at me, I am still having a blast playing this game..

because NWI don't know what they are doing xD

There should be a very slight delay between pulling the trigger and firing with any of the MGs in the game. They fire from an open bolt, so when you pull the trigger the bolt will run forward, chamber a round, fire, recoil, and eject the casing. When the trigger is released, the bolt will stay to the rear. The Uzi works the same way.

The delay is only as long as it takes the bolt to run forward - pretty much the same amount of time it takes the bolt to snap forward on any rifle or pistol when hitting the bolt release. The effect is slightly more obvious in real life, as you can feel the moving bolt shift the weight of the gun between pulling the trigger and the gun firing.

@PhobosAE Honestly, the firing delay on both the M240B and the MG3 is the number one reason why I never use those weapons on Frenzy.