Mr. Chops:
Alas, the explanation for the folly of the magnum shot charge was discerned and revealed by none other than Maj. Burrard in 1930. If you have a copy of "in The Gun Room," I refer you to pages 78 and 80. The former stating that high velocity is no advantage at all at most any game ranges due to increased air resistance, and the latter stating that any hit over 50 yards with even a full choke 12-bore is pure luck.

I trust the Major... even today.