It replaced the AK-47 from former and future titles. The rifle becomes available to buy at Ammu-Nation after the mission "Guardian Angels". Being an assault rifle there is no auto-aim but can be manually aimed. Its performance is similar to that of the more expensive M4, the main difference being that it has a significantly slower rate of fire (400 RPM for the Ruger versus 600 RPM for the M4). The weapon is based on the real life Ruger AC556F law-enforcement version of the Mini-14 rifle.
The Ruger/Kruger can be auto-aimed at pedestrians by setting yourself on fire and holding the targeting button. This can also be done with the M4 and the M60. It is best used after completion of Firefighter side-mission to gain fire-proofing of Tommy.