The B5 Systems Sierra K is a purpose-built compact stock designed for PDW and short-barreled rifle platforms where real estate is tight and every ounce counts. Built for shooters running AR pistols, short-stroke systems, or other compact weapon builds, the Sierra K delivers a slim cheek profile and reduced footprint without sacrificing the controls and mounting points you need in the field. The FDE (Flat Dark Earth) finish blends durability with a modern aesthetic that works across tactical, hunting, and precision rifle setups.

What sets the Sierra K apart is its thoughtful engineering for compact platforms. The low-profile adjustment latch won't snag on gear, slings, or your plate carrier. Internal tensioners maintain a solid, rattle-free fit on the receiver extension, while the integral fixed sling mounts and QD rotation system give you flexibility in how you run your gun. The anti-slip buttpad keeps the stock planted whether you're working from a bench, barricade, or support bag.

The Sierra K mounts via a shortened compact Mil-Spec receiver extension (sold separately as the Sierra K Receiver Extension Kit), so confirm compatibility with your specific platform before ordering. All hardware is color-matched steel with Mil-Spec materials and finishes throughout—no plastic where it doesn't belong. If you're building or upgrading a compact AR platform and want a stock that's been engineered for purpose rather than just scaled down, the Sierra K is worth serious consideration.

Key Features

• Low-profile adjustment latch—snag-free operation in tight spaces
• Slim cheek profile optimized for compact weapon systems
• Integral QD sling mounts with limited rotation for secure attachment
• Internal tensioners eliminate rattle and maintain fit
• Anti-slip buttpad for stable shoulder contact
• Color-matched steel hardware throughout
• Mil-Spec materials and finishes
• FDE finish

Specifications

Brand	B5 Systems
Model	Srk1656 Sierra K
Color	FDE (Flat Dark Earth)
Mounting System	Sierra K Receiver Extension (compact Mil-Spec)
Sling Mounts	Integral fixed QD with limited rotation
Hardware	Color-matched steel, Mil-Spec finish

Frequently Asked Questions

What receiver extension does the Sierra K mount to?

The Sierra K is designed for a shortened compact Mil-Spec receiver extension. You'll need B5 Systems' Sierra K Receiver Extension Kit for proper fitment. Standard full-size extensions are not compatible.

Is the Sierra K suitable for short-barreled rifles and AR pistols?

Yes. The Sierra K is purpose-designed for compact weapon platforms, including PDWs and short-barreled systems where a full-size stock adds unnecessary length and weight.

Does the Sierra K come with QD sling mounts?

Yes. The stock features integral fixed sling mounts with QD capability and limited rotation, allowing you to run your sling without additional adapters.

What finish is the FDE Sierra K?

FDE stands for Flat Dark Earth—a neutral tan finish that pairs well with modern tactical and hunting setups. All steel hardware is color-matched to the stock.