I know someone, or everyone is going to say "Duh, dumbass" by the time this is all through, but.....
What purpose does this little notch serve?

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I am in the middle of my first real ground up build, and I was assembling the bolt today. Ejector, extractor, no problems, but when I put the spacer behind the bolt and went to insert it into the bolt body, this "notch" is stopping the bolt head short from lining up with the cross pin. I pulled a bolt from another 110LA and the notch is in the same spot...did I get the wrong bolt head from Midway (Bolt Head LA RH Push Feed Small Hole)?? someone educate me.