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Measuring muzzle wear and throat erosion

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    Measuring muzzle wear and throat erosion

    Hi, I was checking the wear on my newly acquired 308 Garand (not Navy), and it measured 2.5 MW and about 2.5 TE. But I had some pin gauges in .301" and .302". So I put the 0.301 in and it went right through easily with no friction. I then tried 302 and it was a much tighter fit but with only a tiny bit of pressure from an Otis cleaning cable, it almost went through the whole barrel to within about 2" away from the chamber, I did not want to apply any real pressure, so pushed it back out the muzzle. The barrel looks very clean and shiny, so it sounds like it might have come from the factory at .302"? Does that mean that it actually has almost no erosion and is just oversized? Does it mean anything regarding its capability for accuracy, since the gas pressure will still be even all the way through the bore and the bullet will be spun?
    Last edited by lp1911; 07-19-2021, 08:44 PM.

    #2
    I have seen brand new USGI barrels in wrap, never installed that had a muzzle of 2.5

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      #3
      Originally posted by Orlando View Post
      I have seen brand new USGI barrels in wrap, never installed that had a muzzle of 2.5
      Since the grooves are 0.308" and the lands in my case seem to be ~0.302", that means the rifling is only 0.006" tall (0.003" each land). I am guessing that barrels like that will have a shorter life as the lands wear... I don't however know what that means for accuracy. I am not an expert in this but I think that wear at the muzzle is only meaningful if it means the lands are shallower near the muzzle and since the bullet is shaped by the lands further down the barrel, gas starts to escape around the bullet, but if the entire barrel is oversized, then the real muzzle wear is the difference between the muzzle size and the bore size. So for MW of 0.3025" and a bore of 0.302", then real wear is only 0.0005" (0.00025" on each land), and so the accuracy should be good. Not sure I am a good enough shot to realize that accuracy...
      Last edited by lp1911; 07-30-2021, 12:54 PM.

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