B5 Systems Sierra K Receiver Extension Buffer Tube Kit
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MSRP
$128.99
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28% off
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Updated
Jun 25, 2026
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Includes a Short Heavy Buffer (3.5 oz), Extra Power Spring, Castle Nut and QD End Plate.
Reduced-length 5-position Receiver Extension Constructed of 7075 Aluminum
Specifications
Description
The B5 Systems Sierra K Receiver Extension Kit is the proprietary mounting system for the Sierra K Buttstock. It consists of a reduced-length, mil-spec diameter, 7075 aluminum, 5-position receiver extension, a short heavy buffer (3.5 oz), extra power spring, castle nut, and quick disconnect end plate. All parts are made of mil-spec materials and finishes.
