Your right to a point but I dont think much has changed in the caliber wars today verses then. The calibers he had then are the same calibers today and other than bullet advancement, his reasoning still holds up to today's calibers. If anything bullets have gotten better and would have only further the 270 to JOC. JOC did kill ALOT of game with the 30-06, 7mm Rem mag, 300 Weatherby, 375 H&H mag. He talks about the 30-06 and 270 almost interchangeable in all his books. He also spoke interchangeable as "the three sister" the 270, 280, 30-06. JOC did kill more with the 270 but also killed ALOT with the other calibers. The reason the 270 was Jack's favorite was its superior ballistic coefficient. This is why he is considered the ultimate rifleman. The guy knew first hand what most all the other calibers could do because he killed ALOT with them as well. He loved these non magnum calibers and would demonstrate time after time about their killing power. One of his favorite stories demonstrating why he didn't need a magnum for North American game was when he killed a large Grizzly bear with his 30-06 and he could watch the bullets exit the bear on the far side and hit the rocks of the creek bed. He used a similar example with his 270 shooting a bull elk and watching the large bulls fall time after time in its own shadow dead instantly where they stood. His wife Eleanor was also a very accomplished hunter herself and used many calibers as well. Everyone likes to pigeon hole JOC as a one caliber guy but he was far from that. When the O'Connor's went to Africa, they always took a 270 and 375 as his staple guns with a few others on various occasions. The 270 Win was his self admitted personal favorite and because he adored the pre 64 Winchester Model 70 platform. He was furious with what Winchester did to the Model 70 post 64.

This is interesting regarding today's Ballistic Coefficient. The 270 has more in common performance wise with the 300 Win Mag with its advancement in loadings. Look at the bullet speed,energy and trajectory at 500 yards. This is from Hornadys 2013 ammunition catalog.