The service rifle can fire a total of about 1,995 standard rounds, the equivalent of 100 reloads, from full condition before breaking. When modified with the forged receiver, it can fire a total of about 2,995 standard rounds, the equivalent of 150 reloads, from full condition before breaking.
This rifle, along with two ammunition boxes can be found in a small, unmarked coyote den west of Primm (exact location would be further west from the drive-in cinema and playground, just south of the canyon wreckage spot on the map) guarded by at least two coyotes.
Sometimes in V.A.T.S., the service rifle will disappear from the player character's hands; the animation will continue, however, which will waste ammunition, and do no damage to the enemy. The gun will reappear when the V.A.T.S. animation ends. This glitch may happen outside V.A.T.S. as well, when crouching, but can be fixed by simply standing up. [verified]
When completing the aid for Camp Guardian a loop can be created through dialogue with Private Halford to obtain 1 service rifle, 15 armor piercing 5.56mm rounds and 32 5.56mm rounds by going through the top dialogue options repeatedly. [verified]
When upgraded with both the upgraded springs and the forged receiver, shooting with surplus ammunition makes the Condition jump to 100% before it starts to decline. The condition drops to a certain point around the 75% mark on the scale and then jumps to 100% Condition making 5.56mm surplus ammunition much more valuable as a repair exploit. The process is repeatable. [verified]
A service rifle model with the forged receiver modification
A service rifle model with the reflex sight modification
A service rifle model with the bayonet modification
A service rifle model with all the modifications, including cut content