One of the Staion Commanders at Lyneham had the bright idea to remove the externals from some a/c. When Group heard of this thet went ballistic and the tanks were swiftly replaced. TT and drag they were indeed 914C (round) shackles something we learned the hard way when we first got the Herc. The checklist only specified '914 ' so ne day a one ton auto drop got airborne with the load rigged with 914G shackles (more oval shaped). Come green on and as the load trundled aft these shackles twisted on the anchor cable and jammed. We learned about the difference from that !