The T44 prototype service rifle was not principally designed by any single engineer at Springfield Armory, but was a conventional design developed on a shoestring budget as an alternative to the T47. With minimal funding available, the earliest T44 prototypes used T20E2 receivers fitted with magazine filler blocks and re-barreled for the 7.62×51mm round, with the long operating rod/piston of the M1 replaced by the T47's gas cut-off system. Lloyd Corbett, an engineer in Harvey's rifle design group, added various refinements to the T44 design, including a straight operating rod and a bolt roller to reduce friction.