A3 Industries Stribog Polymer Lower (CZ Scorpion Mags + AR FCG)

The A3 Industries Stribog Polymer Lower is the platform-conversion upgrade for the Grand Power Stribog. The factory Stribog uses a proprietary magazine well and a proprietary fire control group; the A3 lower replaces both with widely available aftermarket alternatives. The lower accepts CZ Scorpion-pattern magazines (PSA 35-rd is the recommended mag, with Magpul 35-rd as a workable second choice) and standard AR-15 fire control components: trigger, safety selector, and pistol grip.

A3 manufactures the lower from injection-molded Zytel polymer with 30 percent glass reinforcement, paired with a machined 7075 aluminum bolt release lever (hard-coated black) and an A3-designed polymer mag release. Ball-detent takedown pins replace the factory cross-pin setup. The serialized portion of the Stribog remains the upper, so this lower ships without an FFL transfer.

Two important compatibility notes. First, this lower is for 9mm Stribogs only; the 10mm and 45 ACP variants use different bolt geometry and are not supported. Second, only AR-15 single-stage triggers will work. Two-stage triggers (Geissele SSA, LaRue MBT-2S) will not reset properly because of the Stribog bolt timing. ALG ACT, single-stage CMC, and Rise Armament single-stage triggers are the recommended options. PSA 35-round Scorpion magazines feed reliably without modification; Magpul 35-rd may require minor feed lip filing; CZ factory magazines fit loose and feed temperamentally; ETS 40-rd may drop the last one to two rounds; 50-round drums are NOT compatible.

At $199.95 direct from A3 Industries, this is the budget alternative to the higher-priced Safety Harbor Firearms Stribog AR Lower ($300+). For Stribog owners who want Scorpion magazine compatibility without buying a factory SP9A3-G, the A3 lower is the value play.