The SR-1 is described in game as:

Police across Europe use this bolt-action bullpup.

It can be found in Koani province, on the far western edge of the map where there’s a nearby Gasoline Drop side mission to steal a helicopter.

There are a handful of cartel here, for the helicopter side mission. They’re easy to take out even without much cover but there are piles of salt to hide behind. The gun case is in an old open-air shack.

This is a long range, highly accurate bolt-action sniper with high penetration. But it has a low rate of fire and is slow to reload. It accepts most sniper rifle accessories, but no buttstock, and being bolt-action it has no select fire options.

The 5 round standard magazine is small, but a 10 round extended magazine can be found in Remanzo province.