This is how the lower is milled. It is typical. They have bored the hole for the postal grip to be fitted. There is just a little bit of material that has got to be shaved if just trying to fit the upper onto the 80% receiver. Once you were to place it on an 80% jig you will notice that the very first hole has only about half of the hole size has material in it and the other half has been drilled out for the postal grip. Not sure why it is like this now, but it is. There is nothing defective with the lower 80%. Must just be there way of complying with regulations.