B5 Systems Srk1655 Sierra K Black
$57.95
$61.00
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$3.05
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The B5 Systems Sierra K is a compact rifle stock purpose-built for PDW platforms and short-barreled AR systems where space is at a premium. If you're running a SBR, pistol-caliber carbine, or other compact rifle setup and need a stock that won't add bulk or snag on gear, the Sierra K delivers a slim, purpose-driven profile designed around the realities of close-quarters and vehicle-based shooting. Its reduced footprint and streamlined cheek rest make it a natural fit for operators who prioritize maneuverability over traditional rifle ergonomics.
The Sierra K mounts via B5's shortened compact Mil-Spec receiver extension, so compatibility starts with confirming you have the right platform—this isn't a universal fit. Once mounted, you get a rock-solid platform with internal tensioners that eliminate rattle and keep the stock locked in place. The adjustment mechanism is stripped down to essentials: a low-profile latch that won't catch on plate carriers, sling mounts, and an anti-slip buttpad that stays put whether you're shooting from barricades or vehicles. Hardware is color-matched and finished to Mil-Spec standards, so you're not sacrificing durability for the compact form factor.
The Sierra K isn't designed to maximize cheek weld or comfort during long shooting sessions—it's engineered for the job it does: keeping your compact rifle light, snag-free, and ready to move. For PDW builds, short-range defensive carbines, or specialized tactical setups, this is a no-nonsense choice from a brand with deep roots in AR ergonomics and combat application.
Key Features
- Compact profile optimized for PDW and short-barreled rifle platforms
- Slim cheek design minimizes snags with gear and clothing
- Low-profile adjustment latch for streamlined operation
- QD and fixed sling mounts built in
- Internal tensioning system for rattle-free lockup
- Anti-slip buttpad for secure shoulder contact
- Mil-Spec materials and finishes throughout
- Color-matched steel hardware
Specifications
| Brand | B5 Systems |
| Model | Sierra K (SRK1655) |
| Color | Black |
| Mount Type | Sierra K Receiver Extension (compact Mil-Spec) |
| Adjustment Type | Low-profile latch |
| Sling Mounts | QD (limited rotation) and fixed integral mounts |
Frequently Asked Questions
What receiver extension do I need for the Sierra K stock?
The Sierra K requires a shortened compact Mil-Spec receiver extension. Standard rifle extension tubes will not work. You'll need to verify your upper is set up for a compact extension or obtain the B5 Sierra K Receiver Extension Kit.
Is the Sierra K right for a standard AR-15?
No. The Sierra K is purpose-built for compact platforms and PDWs that use shortened receiver extensions. It's not compatible with standard Mil-Spec rifle-length tubes used on full-size AR-15s.
What sling attachment options does it have?
The Sierra K includes both a QD (quick-detach) mount with limited rotation and integral fixed sling attachment points, giving you options for how you want to run your sling.
Does it reduce recoil impulse?
The Sierra K is designed for compact weapon systems where space is the priority. It does not include a buffer or recoil mitigation system—that function is handled by your receiver extension and buffer setup.
