AR-15 Pivot Pin Detent Spring

Front Pivot Pin Spring

This United Defense spring sits behind the front pivot pin detent in an AR-15 lower receiver. The pivot pin is the hinge that lets the upper receiver swing open from the lower. The spring pushes the small detent plunger against that pin so it stays put and does not slide out when you break the rifle open for cleaning. It suits a lower build or the replacement of a spring that went missing during assembly, which is common because this part tends to launch across the bench.

Features

• Compression Coil Design — A long, tightly wound coil resists being squashed, which is what keeps steady outward pressure on the detent.
• Pivot Pin Retention — That pressure holds the detent in the pivot pin's groove, so the pin stays captive when the upper is hinged open.
• AR-15 Lower Receiver Fit — Made for the front pivot pin detent channel, the small hole drilled into the front of the lower receiver.
• Bright Metal Finish — The plain, uncoated metal finish shown in the photograph leaves nothing to flake off inside the channel.
• Spring Only — This listing covers the spring; the detent plunger and pivot pin are sold separately.
• Build Or Repair Part — Use it to finish a stripped lower or to replace a weak, kinked or lost spring.
• United Defense Part — Produced by United Defense as a commercial replacement component for the AR-15 platform.

Fit And Installation

The spring and detent go into the channel at the front of the lower receiver, and the pivot pin is then pushed through, holding both in place. Because the spring is compressed during installation, many builders use a pivot pin install tool or a clevis pin to keep it from escaping. Check that your lower uses the standard AR-15 front pivot pin layout before ordering.