The Mk249 is described as:
A belt-fed LMG on an M4 lower.
You’ll find this in Malca province, in a train yard to the south. The weapons case is out in the open on a train in the yard.
The proper approach is via a bridge to the north-west, but if you come from the opposite side, it’s very easy. I approached from the village to the south and there are only three or four narcos between you and the weapons case.
As the description suggests, this is pretty much an assault rifle if you look at its stats. The difference being there’s no select fire option – it’s full auto only – and it has a huge box magazine, which means slower reloads.
It seems like a limited LMG, not really specialising in anything. It suffers from the least damage and accuracy of all LMGs but does have the highest handling. Like the Stoner LMG A1 this benefits from accepting many accessories, but I prefer the Stoner for one reason – check out that video to find out why.