Slugging the bore is to determine the bore size, and not necessarily the condition of the bore. A visual inspection should give you an idea of bore condition.
Since a M1 Rifle can only be cleaned from the muzzle, a quick check of the condition of the bore at the muzzle is to insert a loaded M2 Ball round into the muzzle. An excellent bore will show about 1/4" of bullet exposed. I have seen some of the Korean imports (Blue Sky) that would take the round up to the shoulder of the cartridge case. Same holds true for the British .303. This is a No.4 Mk.1 that appears unissued after rebuild.
Not scientific, but applying a know to an unknown. Military cartridge is dated 1945.
Since a M1 Rifle can only be cleaned from the muzzle, a quick check of the condition of the bore at the muzzle is to insert a loaded M2 Ball round into the muzzle. An excellent bore will show about 1/4" of bullet exposed. I have seen some of the Korean imports (Blue Sky) that would take the round up to the shoulder of the cartridge case. Same holds true for the British .303. This is a No.4 Mk.1 that appears unissued after rebuild.
Not scientific, but applying a know to an unknown. Military cartridge is dated 1945.




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