The MK48 is the first Machine gun available in SFH3. It is the default weapon for the Medic class.
The MK48 is pretty much an average machine gun. DPS is a average for a Machine Gun. Rate of Fire and Impact are mediocre, but Accuracy is on the high side for a Machine Gun. Normal magazine size is 70.
Being a default weapon, it is best to replace early. The SAW, with a much faster Rate of Fire, is a good replacement.
Best secondaries are Pistols. Best choice is P99 (Licence To Kill) to have something accurate and relatively effective on long range. Or if you are not satisfied with their damage rate, Crossbow.
If you use it with Mercenary class, best SMG to backup this weapon, and all other Machine guns is UMP 45 or MTAR. They have good impact and great accuracy, which is importrant.
The MK48 is also seen in SFH2. It seems to be the replacement for the SFH SAW. However, the SAW is completely different weapon in this game and appears to be based on KAC Chain Saw machine gun.