AR-15 LPK Takedown Pin Detent

Description

OVERVIEW – CRITICAL MICRO-DETENT FOR SECURE REAR TAKEDOWN PIN RETENTION

The AR-15 LPK Takedown Pin Detent is the small, pointed steel detent that locks your rear takedown pin in place, preventing it from walking out or falling free during firing, handling, and transport. This detent sits in a small channel in the rear of the lower receiver, pushed forward by the takedown pin detent spring, with its pointed tip engaging the machined grooves in the takedown pin shaft. This creates the positive retention that holds your rear takedown pin in two positions: fully closed, locking the upper and lower receivers together for safe firing, and pulled out to the stop, allowing the upper to pivot open for cleaning and maintenance. Without this detent, your takedown pin has no retention — it will slide out freely, allowing your upper and lower to separate unexpectedly, which is a dangerous condition that can cause malfunctions and unsafe operation. If your original detent is lost, damaged, or has a flattened tip, this mil-spec replacement restores the correct snap and secure lockup of your takedown pin assembly.

This detent is precision machined from solid hardened steel with a sharply pointed tip and black oxide finish for smooth engagement and corrosion resistance. The point is ground to the correct included angle to ride smoothly in the takedown pin’s detent grooves without gouging or excessive wear, while providing firm retention. The body is sized to slide freely in the receiver’s detent channel without binding. It is a direct drop-in replacement for all standard AR-15, M4, M16, and AR-10 lower receivers that use mil-spec takedown pin detents, including forged, billet, and 80% lowers. It works with any standard takedown pin detent spring and takedown pin. Whether you are completing a stripped lower build, replacing a lost detent that launched during installation, or keeping essential spares in your armorer’s kit, this detent ensures your rear takedown pin stays secure and functional.

WHY CHOOSE THIS TAKEDOWN PIN DETENT

The micro-part that keeps your rifle locked together.

1. Precision Pointed Tip for Positive Two-Position Takedown Pin Retention: The AR-15 rear takedown pin relies on a detent-and-groove system to stay in place. The takedown pin has two annular grooves machined around its shaft. This detent’s pointed tip drops into those grooves under spring pressure, holding the pin. In the closed position, the tip locks into the groove closest to the head, securing the pin fully inserted through the upper and lower receivers. In the open position, the tip drops into the groove near the tip of the takedown pin, holding the pin pulled out to the stop so it does not fall out completely while you pivot the upper open. The included angle of this detent’s point is critical: too blunt and it will not engage deeply enough, causing weak retention and a pin that walks out under recoil; too sharp and it will dig into the groove, making the pin hard to pull and causing premature wear. This detent is ground to the exact mil-spec point angle for smooth engagement — firm retention with positive snap, yet still allowing the pin to be pulled with thumb pressure when you need to break down the rifle. The polished tip reduces friction and prevents the detent from scratching or galling the takedown pin shaft.

2. Solid Hardened Steel with Black Oxide Finish for Durability: This detent is machined from solid steel and heat-treated for hardness, ensuring the pointed tip will not flatten, mushroom, or wear down after thousands of takedown cycles. Soft detents made from inferior materials quickly develop a flat spot on the tip, resulting in sloppy, weak retention that allows the takedown pin to work loose during firing — a failure you cannot afford. This detent’s hardened tip maintains its shape and engagement for the life of the rifle. The black oxide finish provides corrosion resistance against moisture, oils, and solvents that collect in the rear detent channel, and ensures smooth sliding inside the receiver channel. The body is precision-ground to the correct diameter to move freely without wobble or binding. The base is flat to sit squarely against the detent spring for consistent pressure. Every detent is inspected for tip geometry and dimensional accuracy, ensuring it interfaces correctly with standard takedown pins and provides the secure lockup you need for safe, reliable operation.

3. Essential Spare for LPK Completion and Easy Drop-In Installation: This takedown pin detent is infamous among AR builders as one of the most commonly lost parts in a lower build — along with the takedown detent spring, it is under spring tension during buffer tube installation and launches across the room if your hand slips. That is why experienced builders and armorers keep multiple spares. Installation is straightforward: drop the detent into the small hole in the rear of the lower receiver (pointed end toward the takedown pin hole), insert the detent spring behind it, and then install your buffer tube or end plate to capture the spring and detent. Then slide your takedown pin through the receiver, and you will feel the detent snap into the grooves. No fitting, gunsmithing, or special tools required — just a standard armorer’s wrench for the buffer tube. Compatible with all standard AR-15, M4, M16, and AR-10 lowers using mil-spec components. Whether you lost your detent, are assembling an 80% lower, or stocking your workbench, this detent restores correct, secure rear takedown pin function.

RESTORE SECURE REAR TAKEDOWN PIN LOCKUP

The AR-15 LPK Takedown Pin Detent delivers hardened steel construction and precision-pointed geometry for reliable rear pin retention.

SPECIFICATIONS

Type: AR-15 LPK Takedown Pin Detent – Rear Takedown Pin Retention Detent. Material: Solid Steel – Heat Treated / Hardened. Finish: Black Oxide – Corrosion Resistant. Tip: Precision-ground pointed tip for Detent Groove Engagement. Function: Engages Grooves in the takedown pin to hold the pin in Open/Closed Positions – Works with Detent Spring. Compatibility: All Standard AR-15 / M4 / M16 / AR-10 Lower Receivers Using Mil-Spec Takedown Pin Detent. Installation Location: Rear Detent Channel of Lower Receiver – Captured by Takedown Pin Detent Spring and Buffer Tube / End Plate.