I have a 1911 GI that I built myself on a RMT frame, And the slide group is definitely different from my GI slide group! The obvious being the bbl is 3.5" on the zg51. The recoil spring plug is positioned in the slide from the rear instead of from the front like all std. 1911's. There is a inner and a outer recoil spring, and the spring guide is shorter. Im either missing a part here or my assembly technique is wrong!! The springs are so tight that they flex in the middle and bind up in the frame when slide is attached. Heres the parts I have and all are auto ordnance factory parts.
ZG51 3.5"bbl, slide, recoil spring plug, guide, inner/outer springs and bbl bushing. Is something missing? I didnt have any trouble with my GI .45 and it shoots great! Ive never had a commander or officers model apart(dont own one) so Im not familiar with them internally!