Don't judge it by TE alone. I may have posted it earlier, but have a SA 1-52 barrel gaged for the NM program still in the grease which measures just under 3.0. It came out of Red River Arsenal in the late 1960's or early 1970's. Major Culver wrote a paper on the development of the M1 NM rifles, and a photo of the barrel marking is in his paper.