The ides of belt fed is for sustained automatic fire, as in for a "true" (military definition) machinegun. In sustained fire, there are issues with things like overheating barrels and cook-offs, so another desired feature would be a quick change barrel. Still a third would be open bolt operation. A M16 will reach cookoff temperature after 120 rounds of automatic fire at the cyclic rate with an air temp of 75 degrees F. Yes, there are/were squad support weapons like the RPK and Israeli FNFAL and even the M14 that operate from the closed bolt, but they really aren't that effective. The whole concept of a belt fed closed bolt weapon with no quick change barrel ability makes no sense at all from where I'm sitting, and even less if it doesn't have full automatic capability.