FWIW, I do know there's a technical distinction between true selective fire assault rifles and what was defined under federal law as "semi-automatic assault weapons"; I own both types.
That said, I don't think you'll win what is inherently a debate on gun control, freedom, and Constitutional rights by bogging down in a technical discussion and semantics over whether an "assault rifle" is full automatic or semiautomatic. Both types are legal and available in the US, and your anti-gun friends are not going to say "Oh, its only semi-automatic not full automatic? Well that changes everything." Not going to happen. They know what an AK47 looks like and whether its semi or full, or whether you call it an AKM, AK47, AKS, or an RPK, its still just a big scary gun to them. You could call it a "semi-automatic ham sandwich" if you wish, but they'll still only see 'big scary gun' and ask why you need a "semi-automatic ham sandwich".