Doc Sawbones in Camp Golf always has one for sale, along with ammunition.
Blake at the Crimson Caravan Company sometimes sells them.
Johnson Nash sometimes has one for sale in Primm.
Gun Runners - can be bought from Vendortron.
Dhatri, Klamath Bob, Duke, Halford and Gomez all carry one.
Jacobstown - inside one of the bungalows, above the fireplace.
Camp Guardian caves - located on the path down the center.
Bloodborne cave - found just after second campfire, next to a dead NCR trooper.
Boulder City - located on the second floor of a abandoned building to the north-east of the Boulder City ruins entrance, next to some skeletons and a ranger holodisk message.
South Vegas Ruins - found on the second shelf of metal racking, located inside the ruined building directly north-east of the entrance to Vault 3.
Survivalist's rifle Honest Hearts, a unique and incredibly powerful service rifle which uses the 12.7mm round and a ten round magazine.
This would have added a melee aspect to the firearm, but the system was never created.
Service rifle bayonet, cut from the game.
It likely would have added an alternative sight with enhanced zoom.
Service rifle reflex sight, cut from the game.
Service rifle forged receiver, +50% condition.
Service rifle upgraded springs, +30% rate of fire.
It also has two swivels, located on the bottom of the stock and ahead of the handguard, which would be used for a sling, but no such sling is present. One extremely useful trait of the service rifle is its ability to repair high-end weapons like the light machine gun, sniper rifle, and assault carbine using the Jury Rigging perk. This also means NCR troopers are far more effective in combat, with a squad able to project a much greater amount of firepower. Additionally, it has low skill and strength requirements, making it a very viable weapon for low level players. As of patch 1.3.0.452, the weapon has dramatically increased rate of fire along with increased accuracy. The service rifle is a moderately powerful mid-tier rifle using the common 5.56mm round as ammunition. Characteristics File:Service Rifle blown up.png