B5 SIERRA K STOCK BLACK

Description

The B5 Systems Sierra K is built around one specific purpose: keeping an AR-pattern carbine as short and manageable as possible without sacrificing a solid cheekweld or practical sling attachment. It is aimed at shooters running compact or PDW-style configurations where a full-length or even standard carbine stock would add bulk that defeats the point of the build.

Rather than the mil-spec buffer tube found on a standard carbine, the Sierra K is designed around B5’s own Sierra K Compact Mil-Spec Receiver Extension Kit, which must be purchased separately. That dedicated extension is what allows the stock to achieve its compact profile — the geometry is not compatible with a standard carbine tube, so the two components are a matched system rather than interchangeable parts.

Sling attachment is handled on both sides of the stock through ambidextrous QD sling mounts. B5 includes both fixed and limited-rotation cup options, which gives the shooter the choice between a sling that stays positionally stable and one that can pivot to reduce binding during transitions or movement. Having both orientations available on a single stock without adapters or aftermarket additions keeps the setup clean on a platform where overall length is already a primary concern.

At 6.6 ounces, the stock itself contributes minimal weight to the build, which matters on a short-format carbine where every ounce is accounted for. The finish is black, consistent with B5’s standard product line. If you are assembling or converting a rifle around a compact receiver extension, the Sierra K is a purpose-matched component rather than a general-purpose stock adapted to fit.