Let me try again...
In the DPMS Southpaw upper receiver: The ejection port is on the left side. Therefor, spent cases eject to the left, which is the OPPOSITE of the standard we normally recognize.
1) The southpaw upper uses a special bolt: Is the bolt track (that funny groove in the top, under the gas key) machined on the opposite side, that is, in a mirror image to the normal GI-type carrier? (This would make the bolt rotate in the opposite direction)
2) Is the bolt itself different than the "USGI-type"? (i.e. is the hole for the cam pin drilled at a different angle?)