Why does getting a heavier bullet help improve "tractability" as one approaches the trans-sonic zone? This question presumes that the rifling on the barrel is too fast for Rex's approach to passing through the trans-sonic zone.
Related question: I know that heavier bullets require faster spin, but I don't know why. Is it the weight or the length that necessitates more spin? This is mentioned about half way through part 75. How does the extra weight help? Spins longer faster of slow spin?