The MG121 is described in the game as:

Your general purpose machine gun.

It’s located in south-west Itacua province, in the ruined buildings of a Santa Blanca outpost. The weapons case is in under some netting in a ruined building next to the helicopter.

The outpost isn’t huge, but it has a road running through it, so there’s a checkpoint, there’s a sniper tower and being on an elevation it has several tiers. This being Itacua, it doesn’t really matter how you approach this – you could have some fun and go loud, or you could start with the sniper and tactically pick off the bad guys.

This is probably the first LMG you’ll pick up. For a long time I dismissed LMGs as being loud and unwieldy, however they all have one huge benefit, which is they make very short work of vehicles.

Firing the MG121 its vertical recoil is very manageable but it does bounce around left and right a little. This gun has full-auto and three round burst fire selections. It accepts a lot but not all accessories for LMGs, with no extended magazine or suppressor available. The standard magazine is 90 rounds.