That is REALLY strange about the left drift from a RH-twist bore, and is contrary to similar tests conducted with the trapdoor. I'm guessing there were factors such as whip, or some other harmonic of which they were either unaware or did not test. Could the offset mass of the magazine have had any effect, I wonder? SA used RH and LH barrels to test the TD. I own one of the the LH carbines.