In fulfilling a contract for 25,000 U.S. Army rifles (Model 1841) and a like quantity for the British government, Robbins and Lawrence were the first to achieve interchangeability of parts on a fully practical level, contributing greatly to all subsequent mass production of machine products. This was made possible by the systematic improvement and refinement of existing standard and special-purpose machine tools, enabling them to perform with the close-limit precision essential for "repeatability" and thus interchangeability (see the American Precision Museum). Simultaneously the firm introduced the milling machine and the turret lathe into routine commercial usage for production manufacturing. The social implications of this technological revolution have been universal.