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gyvel · December 5, 2011, 08:09 PM

It seems the problem with "Blue Sky" markings on M1 carbine barrels was that they apparently used at least a 30 ton hydraulic press or a 20 pound sledge hammer to stamp them and caused indentations that extened through to the bore.

December 5, 2011, 08:09 PM	#5
gyvel Senior Member Join Date: August 30, 2009 Location: Northern AZ Posts: 7,172	It seems the problem with "Blue Sky" markings on M1 carbine barrels was that they apparently used at least a 30 ton hydraulic press or a 20 pound sledge hammer to stamp them and caused indentations that extened through to the bore.