I’m not sure how the Grand Slam would rate to the Leupold VX II but I have a Leupold Euro 3-9 x 50 mm and would have to say the Weaver out performs my Leupold. The Grand Slam is noticeably clearer then my Leupold... The Weaver Grand Slam 4-14 x 40 mm would work well for your 223. I just wish you could have the Nikon to make a comparison for your self. I have nothing negative to say about Nikon scopes because I really like my Nikon Gold for hunting heavy cover in low light conditions. Either one should work well...