M1 Carbine Receiver and Bolt Dimples

[NavyEngineer]

I pulled a few of my carbines out of the safe today to inspect and oil them, when I noticed a small dimple on the receiver and bolt of my IBM M1 Carbine. I did a search, but didn't see a previous thread on this. My guess is that the dimples were used to verify the hardness of the metal - does anyone know if this is the case, or if they signify something else? Thanks in advance.

Information

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[Newscotlander]

Marked after proof firing.

[NavyEngineer]

Marked after proof firing.

Thanks! I've begun to pay more attention to the markings on my old military weapons, and still have a lot to learn about them.

[Bill Ricca]

Definition: Proof Firing is firing a high pressure round to test safety. Each carbine barrel, bolt, and receiver were tested. Sometimes you will find more than one punch mark due to a spare bolt being assembled in a carbine. Below is a picture of proof firing a complete carbine on the left, and a spare barrel on the right.

Notice the safety set up and both will be firing remotely, from a distance, with a protective cover.

[Bubba-7]

Bill,
Remember the picture you posted from the "PM" magazine for the M-14 on old CSP? It showed the locations.

[Bill Ricca]

Bubba: I am not sure what the post was. Below is one from a few years back.

Here is my post from the M14 Forum with the necessary pictures:

Proof Firing