Rare 5.56x57 XM645 Flechette

Add a unique piece of military history to your collection with this scarce 5.56×57mm XM645 Flechette Anti-Aircraft (FAA) cartridge, developed by AAI for the U.S. Army’s Special Purpose Individual Weapon (SPIW) program during the 1960s and early 1970s. This experimental round represents a fascinating chapter in Cold War small arms innovation, designed to tackle low-flying aircraft and helicopters with its high-velocity flechette technology.

The XM645 features a brass casing with a green-tipped fiberglass sabot encasing a steel flechette—a fin-stabilized, dart-like projectile engineered for exceptional penetration and velocity (often exceeding 4,000 fps). The cartridge’s design reflects the military’s push for advanced weaponry during the Vietnam War era, with the goal of equipping infantry with a lightweight, high-performance round capable of engaging aerial threats. Headstamped “I V I 69,” this example is in excellent condition, showcasing the white Honeywell compressed puller sabot configuration, a later variation of the XM645 series.

Though the SPIW program was ultimately shelved due to cost, complexity, and practical challenges, the XM645 remains a coveted collector’s item for its innovative design and historical significance. Perfect for advanced military ammo collectors or enthusiasts of experimental firearms technology, this cartridge is a true conversation piece. Comes with a detailed history card referencing its development, as documented in Blake Stevens’ and Edward Ezell’s book The SPIW: The Deadliest Weapon That Never Was. Don’t miss your chance to own a relic from one of the U.S. military’s most ambitious small arms projects!

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