The Sapphire King — Russell A. Reball

A machine . . . With a mind of its own, And only one thing on its mind . . . To Kill It began as a routine mission: transport a handful of prisoners to a secure location. But when their transport vehicle breaks down in the middle of nowhere, Bravo Company's simple detail turn into a tour from hell and a struggle to survive against a mysterious and overpowering force greater than anything they have ever encountered in combat, a force that has mistaken them for the enemy! Now their fate lies in the hands of one of their prisoners -- a gunlord's son -- whose extraordinary skill may be the only chance any of them have.