NPM with IBM barrel pic needed......

[BrianQ]

Every single prime contractor used a different style or size barrel proof mark to indicate the carbine was proof fired. This is one of the ways one can tell if the barrel is likely the original one or if it has been replaced during a rebuild or restoration. There is more to it than finding a barrel made by the appropriate manufacturer with the right date. This is one of the issues most restorers over look. NPM used a punch mark, probably the same tool they used on the bolt and receiver. The location may or may not be near the barrel manufacturers proof. In fact depending on the barrel manufacturer and the time frame the barrel may not have another proof mark other than the NPM proof mark.

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