The Maschinengewehr 42 is a light machine gun, available to the German forces in Red Orchestra 2: Heroes of Stalingrad. It was added as a part of the Armored Assault content pack on the 23rd of September 2014.
It is unlocked by reaching Veteran (level 4) Machine-Gunner.
Compared to its predecessor the MG34, the MG42 boasts a higher rate of fire at approximately 1200 rounds per minute and significantly less recoil per shot, while still maintaining a very high damage potential. However some key features of the MG34 have not been carried over. The MG42 lacks an alt fire and can't fire single shots for greater ammunition economy and less overheating. Also, the MG42 can only change its barrel from cover or prone, unlike the MG34 which can be changed regardless of whether standing, crouch, prone or in cover.
Level 25: Belt fed with 100 round belt.
Level 50: 250 round belt.
In-game, it says that the level 50 upgrade is an extra belt of ammo. This is incorrect information. It gives you a total of two belts of ammunition. The one that's already loaded in the gun and one in reserve. Each belt is 250 rounds, giving you 500 rounds in total.