Black River Manufacturing ACX 1913 Collapsible Rifle Stock

The Black River MFG ACX 1913 Collapsible Stock is an all-aluminum collapsible stock that mounts to any 1913 Picatinny rear interface. The body is machined aluminum throughout (no polymer load-bearing parts), the buttplate is rubber with a honeycomb texture for grip on a plate carrier, and the QD sling socket runs through the tail. Length of pull adjusts across 9 positions through a familiar carbine-stock collapse mechanism rather than a hinge.

The standout feature is the ambidextrous tail hook on the upper rear of the stock, which gives shooters a positive cheek/shoulder index point similar to the Gear Head Works Tailhook geometry but built into a 1913-compatible stock body rather than a buffer-tube brace. Both left- and right-handed shooters can grip the hook without flipping or reconfiguring the stock.

Mount it on any 1913 host: Sig MPX/MCX, Stribog with factory 1913 adapter, Scorpion with HBI 1913 adapter, Kuna, B&T APC9 and GHM9, AR pistols with 1913 endplates. This is a stock (not a brace) and requires an SBR-configured host. The brace variant (bracx-1913-brace) shares the same chassis with a soft cuff in place of the buttplate for pistol-configured builds. Available in Black, FDE, OD Green, Coyote Brown, Gray, RAL 8000, and Carbon Fiber finishes; pricing varies $244-$310 depending on color.