Okay, so I finish my lower and test it 6 different ways to Tuesday, everything looks good. I purchased the upper from Rio Grande Arms (nice people, very helpful). So I go to mate the upper and lower and I can't get the take down pin to go through the upper. Looking through the hole, there's like a millimeter or less of metal where the upper should have just a hole. This is also evidenced by
the scuff marks on the upper resulting from my trying to push the pin through. They just won't meet. I've checked to see if there's something in the way, I've also tried without the BCG and they won't mate to allow the take down pin to go through then either.
It's not the hole size, that works when I took the lower apart to make sure. The pin goes through.
The lower is an Aim Surplus. The upper is Daniel's Defense.
I'm a complete noob here, so any ideas would be appreciated.