AR-15 Detent Spring Kit

The AR-15 detent spring kit contains the small but absolutely critical springs that secure takedown pins, pivot pins, buffer retainers, and safety selectors in AR-15 lower receivers. Despite their diminutive size—typically less than half an inch long—these springs prove essential for proper rifle function and represent the most commonly lost parts during assembly, disassembly, and maintenance. Every experienced AR-15 builder has launched at least one detent spring across the room during a build, making spare kits an essential component of any armorer's toolkit.

These tiny compression springs work by providing constant tension against detent pins, holding components in place with positive click engagement. The takedown pin detent spring keeps the rear takedown pin from walking out during use, while the pivot pin detent performs the same function for the front pivot pin. The buffer retainer spring holds the buffer and spring assembly in place when the upper receiver is removed, preventing the buffer from launching out the back of the receiver extension. The safety detent spring provides the familiar click when rotating the safety selector between safe and fire positions.

Quality detent spring kits include multiple spares of each spring type, recognizing that these components get lost during builds or wear out over thousands of cycles. Springs manufactured from music wire or chrome silicon wire offer superior longevity compared to generic stainless steel springs. While inexpensive—often under $10 for a complete kit—having spares on hand prevents frustrating delays when a spring disappears mid-assembly. Serious builders keep multiple kits in stock, and these springs make excellent additions to range bags and armorer kits for field repairs.