I found this black color harden steel part among some US machine gun parts years ago. I
always thought it was some sort of gage, it is almost the correct length of a 30-06 headspace gage. Problem is that it is just too small in diameter. A few years ago I even posted these photos on another forum - still without any positive answer.

After looking at this part again I noticed something and found the answer which I will post.Attachment 79553Attachment 79554
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