It is powerful enough to take out a Police Maverick from medium range within a few shots.
When reloading, the process can be done almost instantly. If you press B(Xbox) or Circle(PS3) to reload and wait a second then do a combat roll(Press LT and X for Xbox and L2 and square for PS3) you will notice the ammo counter has reset to 54(or 100 if the extended magazine is attached).
The MG takes about 10 seconds to reload. This is completely unrealistic as in reality, a weapon of this size and weight would most likely take a full minute or two to be reloaded.