B5 SYSTEMS SIERRA K RECEIVER EXTENSION KIT
B5 SystemsThe B5 Systems Sierra K Extension Kit is the proprietary receiver extension system designed specifically for use with the Sierra K stock. Engineered for compact AR builds and PDW-style platforms, this kit provides the foundation needed to achieve a shorter overall length without compromising reliability or performance.
The kit features a reduced-length, MIL-SPEC diameter receiver extension machined from durable 7075 aluminum, offering strength and longevity in demanding conditions. A 5-position adjustment system allows for flexible length-of-pull settings while maintaining a compact footprint.
Included in the kit is a short heavy buffer (3.5 oz) and an extra power spring, optimized to ensure reliable cycling in short-barreled and compact configurations. The system is completed with a castle nut and QD end plate, providing secure installation and integrated sling attachment capability.
Built with MIL-SPEC materials and finishes and proudly made in the USA, the Sierra K Extension Kit is an essential component for maximizing the performance and functionality of the Sierra K stock system.
Kit Includes:
- 7075 Aluminum Reduced-Length Receiver Extension (MIL-SPEC Diameter)
- 5-Position Adjustment System
- Short Heavy Buffer (3.5 oz)
- Extra Power Buffer Spring
- Castle Nut
- QD End Plate