AlexanderA
Member
That's the lot number of the material used to make the barrel, in other words the batch of steel.Any idea what the “y50” indicates?
The "Blue Sky" marking indicates that at some point post-1964 it was probably issued to the Korean military. The reason these guns could have been reimported and sold by a private company is that the Korean government paid for them. Guns that were lent to allies for free (such as to Greece), when returned, went back into U.S. government inventory and had to be sold by the CMP. Those lack import markings because they technically never left U.S. custody.
One problem that has been identified with the "Blue Sky" marking is that sometimes it was stamped with so much force as to distort the bore. (This probably happened more often with Carbines than with Garands.) Other times, the marking is so light that it can be removed by careful peening, sanding, and cold bluing.
All of this points to the conclusion that your best alternative is to rebarrel.