Daryl,
Your comments about .30-06 performance on bison is, in my opinion, 100% accurate, as I have repeatedly had similar results with big elk shot with even heavy 220 grain .30-06 rounds; even when shot through the heart, had them run up to around 200 yards. They simply don't do that when shot with .375 H & H, .416 Rigby, .450 NE! Elmer Keith was right, when he spoke about the .30-06 being inadequate for such purposes, for those of you who know what he said. Jack O'Connor, old ".270 Jack" as Keith called him, on the other hand, and his ideas about using the .270 for elk and most everything else, were wrong. It is even worse than the .30-06 for such large animals. I like both the .30-06 and .270, as long as they are used for what they will do best; same with .40 caliber and larger bores.