All because of the machinery they had stored at Winchester. Winchester had asked the government to store all of the machinery used by the other carbine makers at the end of the war at Winchester. The government owned the majority of the equipment. Winchester did not want to stop any of there commercial production so used this equipment to make the replacement barrels. Barrel making equipment from Inland or Rock-Ola or others and the barrel cutting slot equipment from IBM. Didn't matter to Winchester as long as the barrels were good, proofed OK and were accepted by and paid for by the government.