Methods and systems for locking and operating firearms, particularly rifle models that have a safety selector that extends through the width of the weapon body. For example, a safety selector lock can be configured to attach to the lower receiver of an AR-15. A replacement, extended safety selector allows installation of a safety selector lock outside the body of the firearm, avoiding modification of the weapon's firing components. The safety selector is locked by an engagement pin engaging an engagement hole on a locking cap connected to an end of the safety selector, outside the weapon body. Some weapons have two SAFE positions; disclosed embodiments can provide two DIFFERENT SAFE positions—a OPEN SAFE (unlocked) and a LOCKED SAFE. By using an engagement hole with a single opening, the engagement pin engages the engagement hole, thus locking the safety selector, in only one of the SAFE positions.