engineer, ArmaLite quickly released a number of unique rifle concepts. The first prototypes of the 7.62 mm AR-10 emerged between 1955 and early 1956. At the time, the United States Army was in the midst of testing several rifles to replace the obsolete M1 Garand. Springfield Armory's T44E4 and heavier T44E5 were essentially updated versions of the Garand chambered for the new 7.62 mm round, while Fabrique Nationale submitted their FN FAL as the T48. ArmaLite's AR-10 entered the competition late, hurriedly submitting two hand-built "production" AR-10 rifles based on the fourth prototype in the fall of 1956 to the United States Army's Springfield Armory for testing. The AR-10 prototypes (four in all) featured a straight-line stock design, rugged elevated sights, an oversized aluminum flash suppressor and recoil compensator, and an adjustable gas system. In the fourth and final prototype, the upper and lower receiver were hinged with the now-familiar hinge and takedown pins, and the charging handle did not reciprocate and was not attached to the bolt carrier. For a 7.62mm NATO rifle, the AR-10 prototype was incredibly lightweight at only 6.85 lb empty. Initial comments by Springfield Armory test staff were favorable, and some testers commented that the AR-10 was the best lightweight automatic rifle tested by the Armory. The rifle's aluminum/steel composite barrel (an untried prototype design specified for the tests by ArmaLite's president, George Sullivan, over Stoner's vehement objections) burst in a torture test conducted by Springfield Armory in early 1957. ArmaLite quickly replaced it with a conventional steel barrel, but the damage had been done. The final Springfield Armory report advised against the adoption of the rifle, stating that it would take "five years or more to take it through tests to adoption". While ArmaLite objected, it was clear that the AR-10, a brand-new rifle still in the prototype stage, was at a disadvantage compared to competing designs with longer development cycles, and by 1957, U.S. Army infantry forces urgently required a modern, magazine-fed infantry rifle to replace the M1. In the end, the Army chose the conventional T44, which entered production as the M14 rifle in 1957. That same year, ArmaLite completed about 50 production AR-10 rifles at its workshop for use as demonstrator models for its sales agents, including Samuel Cummings, a famous international arms dealer. Attempts to rush completion of these fifty rifles resulted in a few units that were assembled with