Thank you to everyone that commented concerning the Falkor Defense .308 Ambi Matched Receiver Set. I was finally able to separate the receivers with a bit of rubber mallet persuasion recommended in a prompt reply from Josh Clark at Falkor Defense, and also by survivalshop. I was also informed that tight tolerances are what they are known for, and once assembled, separation gets much easier. Guess I'll find out when I get there.