The B5 Systems Sierra K (brand part no. SRK-1658) is a purpose-built compact stock finished in OD Green, designed specifically for PDW and other compact AR-platform weapon systems. B5 slimmed down the cheek profile and reduced overall size compared to a standard carbine stock, then added a snag-free adjustment lever so it won’t catch on gear during fast manipulation. It measures 5.63 inches and mounts via a shortened, compact Mil-Spec receiver extension, making it a natural fit for shooters building a genuinely compact rifle or pistol setup.

Key Specifications

• Purpose-built as a compact stock for PDW and compact weapon systems.
• Features a reduced overall size and slim cheek profile.
• Uses a snag-free adjustment lever for fast, catch-free manipulation.
• Includes a limited-rotation QD sling mount.
• Also includes an integral fixed sling mount.
• Built with internal tensioners for a tight, rattle-free fit on the tube.
• Finished with an anti-slip buttpad.
• Measures 5.63 inches in length.
• Mounts via a shortened, compact Mil-Spec receiver extension.
• Finished in OD Green.

Frequently Asked Questions

What is the Sierra K designed for? It’s built specifically for PDW and other compact AR-platform weapon systems where a shorter stock and slimmer profile matter.

Does it use a standard Mil-Spec receiver extension? No — it mounts via a shortened, compact Mil-Spec receiver extension rather than a standard-length tube.

What keeps the stock from rattling on the tube? Internal tensioners hold the stock tight against the receiver extension to eliminate play.

Buy the B5 Systems Sierra K Compact PDW Stock, OD Green

A standard carbine stock is still too long for a true compact build, and the B5 Systems Sierra K was designed to fix that. Browse our full AR braces/stocks selection and order from our Lubbock, Texas gun shop for fast, direct shipping.