The SR25 is described in the game as:
Compact for CQB, but accurate at long range.
It can be found in eastern Caimanes province, inside Caimanes Base. Expect sicarios. The weapons case is upstairs inside a building on the east side of the base.
I used a boat to approach via the river to the north of the base. You can enter the base from that side where a fallen tree has broken the wall. Being night time, some of the enemies were sleeping, which reduced the patrols and I only had to eliminate a few sicarios before reaching the building easily. The remaining enemies in the building were also asleep next to the weapons case, so I pistol whipped them before picking up the gun.
While you’re here, you’ll also find the large 50 round 5.56 PMAG magazine for assault rifles in this base.
The description refers to the compactness of the SR25, and while it has good handling, it is beaten there by the MK14 (found in Koani) and SRSA1 (in Mojocoyo). This is understandable as it’s built off an AR platform, however it deals the lowest damage in its class, and all its other stats are kind of average.
On the plus side, along with handling, this is a semi-auto firing rifle, which doesn’t fire as fast as the G28 (found in San Mateo), but it can reload quickly which is certainly beneficial.
The standard magazine holds 10 rounds, and you can pick up an extended 20 round magazine in Media Luna.