I had Shuff park and put a new Krieger GI contour barrel in 308 on my M1 many years back. Rifle always short stroked after a few rounds. I never really did much about it. well i decide to get it out and check everything. Turns out the gas port was only .0865. Min is .0965 max .1060. I drilled it out to .1000 and now it functions fine. No idea why Krieger only drilled it to .0865 on a as advertized 308 barrel.