Zenith Firearms, known for its presence in the HK MP5 clone market, is making significant strides by diversifying its firearm lineup. Their latest offering, the ZF-56, marks an innovative hybrid that blends the familiarity of the AR-15 and HK93 platforms. What sets this rifle apart is its incorporation of a roller-delayed blowback bolt system, a feature favored by enthusiasts. Notably, the ZF-56 retains the convenience of a last-round bolt hold open mechanism but introduces a proprietary lower receiver, while also maintaining compatibility with AR-style triggers, grips, and magazines.