B5 Systems Srk1658 Sierra K Od Green

The B5 Systems Sierra K is a purpose-built compact stock engineered for PDW and short-barreled rifle platforms where real estate is tight and reliability isn't negotiable. If you're running an SBR, pistol-caliber carbine, or other compact weapon system, the Sierra K strips away unnecessary bulk without sacrificing the controls and mounting options you need in the field. Its slim cheek profile and reduced footprint make it ideal for shooters who need to move fast and navigate tight spaces—whether that's a truck bed, a training course, or a defensive scenario where every inch counts.

B5 built this stock around practical ergonomics. The low-profile adjustment latch won't snag on gear or catch when you're shouldering the rifle quickly. You get integrated QD attachment points for sling mounting, and internal tensioners keep everything locked tight under recoil. The anti-slip buttpad grips clothing and shoulder naturally, so you're not fighting the stock when you're behind the gun. It's the kind of attention to detail that separates purpose-driven gear from generic aftermarket parts.

Installation is straightforward—the Sierra K mounts to a shortened compact Mil-Spec receiver extension via the included Sierra K Receiver Extension Kit. All hardware is color-matched steel and finished to Mil-Spec standards, so your OD Green stock and hardware will age and perform together. This is a stock that works as hard as you do.

Key Features

• Compact profile optimized for PDW and short-barreled rifle systems
• Slim cheek design for reduced snag risk during deployment
• Low-profile adjustment latch for fast, snag-free operation
• Integrated QD sling mounts for secure attachment points
• Internal tensioners for solid lock-up under recoil
• Anti-slip buttpad for reliable shouldering
• Mil-Spec materials and color-matched steel hardware
• Ships with Sierra K Receiver Extension Kit for straightforward installation

Specifications

Frequently Asked Questions

What receiver extension does the Sierra K use?

The Sierra K mounts to a shortened compact Mil-Spec receiver extension. The product includes the Sierra K Receiver Extension Kit to complete the installation.

Is the Sierra K designed for full-size or compact rifles?

The Sierra K is optimized for PDW and compact weapon systems where minimal length and profile are priorities. Its reduced size makes it ideal for short-barreled rifles and similar platforms where conventional stocks would be oversized.

Does the Sierra K include sling attachment options?

Yes. The stock features integrated fixed sling mounts with limited rotation QD capability, allowing you to attach slings securely without additional hardware.

Will the steel hardware match the OD Green finish?

All hardware is color-matched to the stock and finished to Mil-Spec standards, so the OD Green appearance is consistent across the entire assembly.