Jaunty-*Laughs* Mini MG 42 then. Okay.
Mat69- Yes, the Swiss variant is the '51.
The "belt holding" is a cure to a symptom. The ammo they're using may be old, and lacking enough oomph to fully kick the bolt back, and drag the next round in.(Seen it with many old MG's, and old surplus ammo)
Shooting a belt fed GPMG off a bench is just silly. Offhand, assault, or prone, that old bitch would not be as "jumpy". Unfortunately, a lot of ranges won't let one fire without using the bench. This may be such a case.
Meplat-