Extremely Rare Vietnam Era Prototype Factory Original German Heckler & Koch HK223 Selective Fire Rifle, Class III/NFA C&R Fully Transferable Machine Gun

An extraordinary centerpiece for an advanced Class III or Heckler & Koch collection, this 1966 HK223 is a registered, fully transferable, factory-original prototype selective-fire rifle—an exceptionally rare developmental link between the H&R T223 and the production HK33.

• Manufactured in 1966, as dated on the left side of the magazine well
• Incredibly rare factory-original Heckler & Koch HK223 prototype selective-fire rifle
• Registered as a fully transferable machine gun, making it highly desirable to NFA/Class III collectors
• Described as the only example of its kind ever offered by Rock Island Auction Company
• Evolutionary precursor to the HK33, representing an important step in Heckler & Koch’s 5.56mm rifle development
• Believed to follow the earlier T223 prototype machine guns, reportedly made in very limited numbers around 1965–1966
• T223 prototypes were associated with Harrington & Richardson under license from Heckler & Koch
• Some sources state the Harrington & Richardson T223 prototypes may have been manufactured by Heckler & Koch and imported by Harrington & Richardson for U.S. military testing
• Period advertising reportedly illustrated early prototype variants with the text: “MILITARY WEAPONS SYSTEMS/Design and Fabrication/Harrington & Richardson, Inc./in association with/HECKLER & KOCH GMBH”
• Reportedly once part of the Harrington & Richardson factory museum collection, which included similar developmental machine guns
• Believed to have been brought into the United States and registered before the 1968 changes to import and registration rules
• Harrington & Richardson sold off its museum collection after the company went bankrupt in the mid-1980s
• Scaled-down design based on the HK G3, which was chambered for the larger 7.62mm NATO/.308 cartridge
• Chambered for the then-new 5.56mm NATO/.223 cartridge
• Uses Heckler & Koch’s roller-delayed blowback operating system, a hallmark of classic HK engineering
• Development of the rifle that became the HK33 began around 1963
• The first prototypes, known as the T223, were completed in 1965
• Harrington & Richardson supplied a small number of T223 prototypes for U.S. Army Small Arms Weapons Systems field experiment testing conducted between 1965 and 1966
• In SAWS testing, the T223 was evaluated alongside the:
  • M14
  • XM16E1
  • AR-18
  • M60
  • AK47
  • RPD
  • DPM
  • Modular Stoner 63 machine gun
• SAWS testing took place after the U.S. Army had already adopted the M16 in 1964, with the goal of identifying the best overall weapon combination for rifle squads
• T223-type rifles were also reportedly fielded experimentally by special forces during the Vietnam War
• U.S. Navy SEALs reportedly acquired a very limited number of these rifles as alternative weapons for their units
• Period photographs are known online showing SEALs carrying early HK/T223-type rifles in Vietnam
• A noted photograph of U.S. Navy SEAL Rudy Boesch is often captioned as showing him holding a Harrington & Richardson T223
• The original description notes the possibility that Boesch may instead be holding a variant closer to this HK223, based on visible differences near the lower front receiver area and the apparent absence of a trigger-guard-area bolt-hold-open lever
• Some T223 prototypes had a bolt-hold-open mechanism and release lever built into the front of the trigger guard
• This HK223 prototype does not have that bolt-hold-open feature, and that feature was not carried into the final HK33 production design
• One reported advantage of these rifles in Vietnam was their ability to use 40-round magazines in addition to 20-round magazines
• At that stage of the Vietnam War, M16 rifles were typically supplied with 20-round magazines
• The added magazine capacity was considered a benefit for special forces users, and T223-type rifles were reportedly well received
• Sights:
  • Hooded post front sight
  • Four-position drum rear sight
• Muzzle device:
  • Birdcage flash hider
• Forearm:
  • Ribbed narrow forearm
• Magazine release:
  • Functional “paddle” magazine release
• Selector:
  • Right-handed selector marked “S/E/F”
• Stock:
  • Prototype buttstock similar to those seen in the limited known photographs of Harrington & Richardson T223 machine guns
• Left side of magazine well marked:
  • “HK 223 – 0242”
  • “1966”
• No markings on the right side or top of the gun
• Replacement HK33-type pistol trigger housing marked on the concealed front surface:
  • “62-426661”
  • “DE 9mm x 19”
  • “HK”
• Receiver, trigger housing, and trigger pack are in “pin” configuration
• Bolt carrier is in original full-auto configuration
• Bolt assembly shows prototype design differences when compared with the later HK33 design
• Magazine is absent

This HK223 stands out as a historically significant, highly collectible prototype with direct ties to Heckler & Koch development, Harrington & Richardson military testing, early 5.56mm NATO experimentation, and Vietnam-era special operations interest.