Just finished service in the norwegian army. The MG3 there was old as dirt and just garbage. 40 years old, only thing replaced were their barrels. Heavy as fuaark, need one gunner and one loader that carries the ammunition in a backpack that is even heavier than fuark. After firing and you opened it up for cleaning, it was dirtier than Jabba the Hut's crapper after a hangover. It jams if you get one corn of sand in there, and it will continue to jam every second bullet if you don't remove the corn.
The recoil... *on target*BRR**off target*RRRRRRRRRRRRR
Every MG gunner and loader hated it, and hated their lives when they had to drag that weapon around. It had it's golden time, but now it is just... Good riddance
The plus is awesome firepower, and the fact that it is the daughter of the MG42.
The army is replacing them with Minimi's now, allowing two(!) MG's in a 8-man squad.