Developing a new operating system is like re-inventing the wheel. Its much easier to improve upon an existing and proven design rather than spend serious $$$ on an unproven design which may be technologically infeasible *BAR10*. Small arms programs in the late 70's and 80's which spawned the G11 and others showed the designers that there was essentially no interest in "new", only in improved. Many weapons borrowed from the AK piston designed and refined it using more precise and modern Western manufacturing techniques. While its clear to see where the Sig 550 series was influenced by the AK, a copy it is not. A closer Sig copy of the AK would be the 540 series, and there is still some deviation. The closest Western copy of the AK was the FN FNC. Look at a dissasembled FNC and compare the pictures to your AK and you will quickly see what I am talking about. IMO, the FN FNC is the best manefestation of the AK design. Its truly an optimized/Westernized 5.56 AK with amazing capability. While not without fault, no weapon is, I believe the FNC to be one of the best combat weapons availible, especially in newer versions like the AK5 or even the AMR. The Sig 550 does not equal AK, though it did take some design ques from it....The FN FNC is your "AK clone".