Just put together my AR15. The upper assembly came completed. I decided to take it apart and see how it all fits together (field stripping, not completely tearing it down). I pulled the little cotter pin, the firing pin and the cam bolt out of the bolt carrier group.

I didn't notice when I took it apart which direction the "sprocket" that locks the bolt in place faces (I didn't take note before I let it spin). Is there a particular direction the flatter spot needs to face or does it not matter?

The flatter spot is the extractor and should point toward the ejection port when it is assembled.

All of my AR's allow the cam pin to go in only one way. The hole on one side is only big enough for the cam pin which keeps the extractor oriented properly. The other side of the bolt is too small for the pin.

They should be like this but some can be missing the little "peened" over lips that allow only one way to reassemble.